net: macb: Use mdio child node for MDIO bus if it exists

This allows explicitly specifying which children are present on the mdio
bus. Additionally, it allows for non-phy MDIO devices on the bus.
Signed-off-by: NSean Anderson <sean.anderson@seco.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -898,6 +898,17 @@ static int macb_mdiobus_register(struct macb *bp)
 {
 	struct device_node *child, *np = bp->pdev->dev.of_node;
 
+	/* If we have a child named mdio, probe it instead of looking for PHYs
+	 * directly under the MAC node
+	 */
+	child = of_get_child_by_name(np, "mdio");
+	if (np) {
+		int ret = of_mdiobus_register(bp->mii_bus, child);
+
+		of_node_put(child);
+		return ret;
+	}
+
 	if (of_phy_is_fixed_link(np))
 		return mdiobus_register(bp->mii_bus);