net: ftgmac100: Add DM_MDIO support

Add support for DM_MDIO to connect to PHY.  For the systems that have a
stand-alone MDIO hardware block, enable CONFIG_DM_MDIO to use driver
model for MDIO devices.

Signed-off-by: Dylan Hung <dylan_hung@aspeedtech.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/drivers/net/ftgmac100.c b/drivers/net/ftgmac100.c
index 0687230..b6e9526 100644
--- a/drivers/net/ftgmac100.c
+++ b/drivers/net/ftgmac100.c
@@ -220,7 +220,11 @@
 	struct phy_device *phydev;
 	int ret;
 
-	phydev = phy_connect(priv->bus, priv->phy_addr, dev, priv->phy_mode);
+	if (IS_ENABLED(CONFIG_DM_MDIO))
+		phydev = dm_eth_phy_connect(dev);
+	else
+		phydev = phy_connect(priv->bus, priv->phy_addr, dev, priv->phy_mode);
+
 	if (!phydev)
 		return -ENODEV;
 
@@ -589,10 +593,16 @@
 	if (ret)
 		goto out;
 
-	ret = ftgmac100_mdio_init(dev);
-	if (ret) {
-		dev_err(dev, "Failed to initialize mdiobus: %d\n", ret);
-		goto out;
+	/*
+	 * If DM MDIO is enabled, the MDIO bus will be initialized later in
+	 * dm_eth_phy_connect
+	 */
+	if (!IS_ENABLED(CONFIG_DM_MDIO)) {
+		ret = ftgmac100_mdio_init(dev);
+		if (ret) {
+			dev_err(dev, "Failed to initialize mdiobus: %d\n", ret);
+			goto out;
+		}
 	}
 
 	ret = ftgmac100_phy_init(dev);