diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
index 4a7a303be2f7..0c6240c4a7e9 100644
--- a/drivers/net/mdio/Kconfig
+++ b/drivers/net/mdio/Kconfig
@@ -185,6 +185,13 @@ config MDIO_IPQ8064
 	  This driver supports the MDIO interface found in the network
 	  interface units of the IPQ8064 SoC
 
+config MDIO_REALTEK_RTL
+	tristate "Realtek RTL9300 MDIO interface support"
+	depends on MACH_REALTEK_RTL || COMPILE_TEST
+	help
+	  This driver supports the MDIO interface found in the Realtek
+	  RTL9300 family of Ethernet switches with integrated SoC.
+
 config MDIO_REGMAP
 	tristate
 	help
diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
index 1015f0db4531..2cd8b491f301 100644
--- a/drivers/net/mdio/Makefile
+++ b/drivers/net/mdio/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_MDIO_MOXART)		+= mdio-moxart.o
 obj-$(CONFIG_MDIO_MSCC_MIIM)		+= mdio-mscc-miim.o
 obj-$(CONFIG_MDIO_MVUSB)		+= mdio-mvusb.o
 obj-$(CONFIG_MDIO_OCTEON)		+= mdio-octeon.o
+obj-$(CONFIG_MDIO_REALTEK_RTL)		+= mdio-realtek-rtl.o
 obj-$(CONFIG_MDIO_REGMAP)		+= mdio-regmap.o
 obj-$(CONFIG_MDIO_SUN4I)		+= mdio-sun4i.o
 obj-$(CONFIG_MDIO_THUNDER)		+= mdio-thunder.o
diff --git a/drivers/net/mdio/mdio-realtek-rtl.c b/drivers/net/mdio/mdio-realtek-rtl.c
new file mode 100644
index 000000000000..27d1bc02e1e0
--- /dev/null
+++ b/drivers/net/mdio/mdio-realtek-rtl.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MDIO controller for RTL9300 switches with integrated SoC.
+ *
+ * The MDIO communication is abstracted by the switch. At the software level
+ * communication uses the switch port to address the PHY with the actual MDIO
+ * bus and address having been setup via the realtek,smi-address property.
+ */
+
+#include <linux/mdio.h>
+#include <linux/mfd/syscon.h>
+#include <linux/mod_devicetable.h>
+#include <linux/of_mdio.h>
+#include <linux/phy.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define SMI_GLB_CTRL			0x000
+#define   GLB_CTRL_INTF_SEL(intf)	BIT(16 + (intf))
+#define SMI_PORT0_15_POLLING_SEL	0x008
+#define SMI_ACCESS_PHY_CTRL_0		0x170
+#define SMI_ACCESS_PHY_CTRL_1		0x174
+#define   PHY_CTRL_RWOP			BIT(2)
+#define   PHY_CTRL_TYPE			BIT(1)
+#define   PHY_CTRL_CMD			BIT(0)
+#define   PHY_CTRL_FAIL			BIT(25)
+#define SMI_ACCESS_PHY_CTRL_2		0x178
+#define SMI_ACCESS_PHY_CTRL_3		0x17c
+#define SMI_PORT0_5_ADDR_CTRL		0x180
+
+#define MAX_PORTS       32
+#define MAX_SMI_BUSSES  4
+
+struct realtek_mdio_priv {
+	struct regmap *regmap;
+	u8 smi_bus[MAX_PORTS];
+	u8 smi_addr[MAX_PORTS];
+	bool smi_bus_isc45[MAX_SMI_BUSSES];
+	u32 reg_base;
+};
+
+static int realtek_mdio_wait_ready(struct realtek_mdio_priv *priv)
+{
+	u32 val;
+
+	return regmap_read_poll_timeout(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_1,
+					val, !(val & PHY_CTRL_CMD), 10, 500);
+}
+
+static int realtek_mdio_read_c45(struct mii_bus *bus, int phy_id, int dev_addr, int regnum)
+{
+	struct realtek_mdio_priv *priv = bus->priv;
+	u32 val;
+	int err;
+
+	err = realtek_mdio_wait_ready(priv);
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_2, phy_id << 16);
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_3,
+			   dev_addr << 16 | (regnum & 0xffff));
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_1,
+			   PHY_CTRL_TYPE | PHY_CTRL_CMD);
+	if (err)
+		return err;
+
+	err = realtek_mdio_wait_ready(priv);
+	if (err)
+		return err;
+
+	/* get_phy_c45_ids() will stop the mdio bus scan if we return an error
+	 * here. So even though the SMI controller indicates an error for an
+	 * absent device don't proagate it here.
+	 */
+	//if (val & BIT(25)) {
+	//	err = -ENODEV;
+	//	return err;
+	//}
+
+	err = regmap_read(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_2, &val);
+	if (err)
+		return err;
+
+	return val & 0xffff;
+}
+
+static int realtek_mdio_write_c45(struct mii_bus *bus, int phy_id, int dev_addr,
+				  int regnum, u16 value)
+{
+	struct realtek_mdio_priv *priv = bus->priv;
+	u32 val;
+	int err;
+
+	err = realtek_mdio_wait_ready(priv);
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_0, BIT(phy_id));
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_2, value << 16);
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_3,
+			   dev_addr << 16 | (regnum & 0xffff));
+	if (err)
+		return err;
+
+	err = regmap_write(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_1,
+			   PHY_CTRL_RWOP | PHY_CTRL_TYPE | PHY_CTRL_CMD);
+	if (err)
+		return err;
+
+	err = regmap_read_poll_timeout(priv->regmap, priv->reg_base + SMI_ACCESS_PHY_CTRL_1,
+				       val, !(val & PHY_CTRL_CMD), 10, 100);
+	if (err)
+		return err;
+
+	if (val & PHY_CTRL_FAIL) {
+		err = -ENXIO;
+		return err;
+	}
+
+	return err;
+}
+
+static int realtek_mdiobus_init(struct realtek_mdio_priv *priv)
+{
+	u32 port_addr[5] = { };
+	u32 poll_sel[2] = { 0, 0 };
+	u32 glb_ctrl_mask = 0, glb_ctrl_val = 0;
+	int i, err;
+
+	for (i = 0; i < MAX_PORTS; i++) {
+		int pos;
+
+		if (priv->smi_bus[i] > 3)
+			continue;
+
+		pos = (i % 6) * 5;
+		port_addr[i / 6] |=  priv->smi_addr[i] << pos;
+
+		pos = (i % 16) * 2;
+		poll_sel[i / 16] |= priv->smi_bus[i] << pos;
+	}
+
+	for (i = 0; i < MAX_SMI_BUSSES; i++) {
+		if (priv->smi_bus_isc45[i]) {
+			glb_ctrl_mask |= GLB_CTRL_INTF_SEL(i);
+			glb_ctrl_val |= GLB_CTRL_INTF_SEL(i);
+		}
+	}
+
+	err = regmap_bulk_write(priv->regmap, priv->reg_base + SMI_PORT0_5_ADDR_CTRL,
+				port_addr, 5);
+	if (err)
+		return err;
+
+	err = regmap_bulk_write(priv->regmap, priv->reg_base + SMI_PORT0_15_POLLING_SEL,
+				poll_sel, 2);
+	if (err)
+		return err;
+
+	err = regmap_update_bits(priv->regmap, priv->reg_base + SMI_GLB_CTRL,
+				 glb_ctrl_mask, glb_ctrl_val);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int realtek_mdiobus_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct realtek_mdio_priv *priv;
+	struct fwnode_handle *child;
+	struct mii_bus *bus;
+	int err;
+
+	bus = devm_mdiobus_alloc_size(dev, sizeof(*priv));
+	if (!bus)
+		return -ENOMEM;
+
+	bus->name = "Reaktek Switch MDIO Bus";
+	bus->read_c45 = realtek_mdio_read_c45;
+	bus->write_c45 =  realtek_mdio_write_c45;
+	bus->parent = dev;
+	priv = bus->priv;
+
+	priv->regmap = syscon_node_to_regmap(dev->parent->of_node);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	err = device_property_read_u32(dev, "reg", &priv->reg_base);
+	if (err)
+		return err;
+
+	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
+
+	device_for_each_child_node(dev, child) {
+		u32 pn, smi_addr[2];
+
+		err = fwnode_property_read_u32(child, "reg", &pn);
+		if (err)
+			return err;
+
+		if (pn > MAX_PORTS)
+			return dev_err_probe(dev, -EINVAL, "illegal port number %d\n", pn);
+
+		err = fwnode_property_read_u32_array(child, "realtek,smi-address", smi_addr, 2);
+		if (err) {
+			smi_addr[0] = 0;
+			smi_addr[1] = pn;
+		}
+
+		if (fwnode_device_is_compatible(child, "ethernet-phy-ieee802.3-c45"))
+			priv->smi_bus_isc45[smi_addr[0]] = true;
+
+		priv->smi_bus[pn] = smi_addr[0];
+		priv->smi_addr[pn] = smi_addr[1];
+	}
+
+	err = realtek_mdiobus_init(priv);
+	if (err)
+		return dev_err_probe(dev, err, "failed to initialise MDIO bus controller\n");
+
+	err = devm_of_mdiobus_register(dev, bus, dev->of_node);
+	if (err)
+		return dev_err_probe(dev, err, "cannot register MDIO bus\n");
+
+	return 0;
+}
+
+static const struct of_device_id realtek_mdio_ids[] = {
+	{ .compatible = "realtek,rtl9301-mdio" },
+	{ .compatible = "realtek,rtl9302b-mdio" },
+	{ .compatible = "realtek,rtl9302c-mdio" },
+	{ .compatible = "realtek,rtl9303-mdio" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, realtek_mdio_ids);
+
+static struct platform_driver rtl9300_mdio_driver = {
+	.probe = realtek_mdiobus_probe,
+	.driver = {
+		.name = "mdio-rtl9300",
+		.of_match_table = realtek_mdio_ids,
+	},
+};
+
+module_platform_driver(rtl9300_mdio_driver);
+
+MODULE_DESCRIPTION("RTL9300 MDIO driver");
+MODULE_LICENSE("GPL");
