+static int lan937x_sw_mdio_read(struct mii_bus *bus, int addr, int regnum)
+{
+	struct ksz_device *dev = bus->priv;
+	u16 val;
+	int ret;
+

It would be good to check for C45 regnum values and return -EOPNOTSUPP.

+	ret = lan937x_internal_phy_read(dev, addr, regnum, &val);
+	if (ret < 0)
+		return ret;
+
+	return val;
+}
+
+static int lan937x_sw_mdio_write(struct mii_bus *bus, int addr, int regnum,
+				 u16 val)
+{
+	struct ksz_device *dev = bus->priv;
+

Same here.

     Andrew