lantiq: etop: pass devicetree node to phy driver

Use of_mdiobus_register() to pass the ethernet phy node to the phy
drivers. This is needed for the at8030 phy driver which needs to know
the GPIO which is connected to the ar8030 reset pin.

This driver expects a child in gsw/etop node named "mdio-bus", which has
the ethernet phys defined:

&gsw {
	phy-mode = "rmii";
	phy-handle = <&phy0>;
	mtd-mac-address = <&ath9k_cal 0xa91>;
	mtd-mac-address-increment = <(-2)>;

	mdio-bus {
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <0>;

		phy0: ethernet-phy@0 {
			reg = <0>;
			reset-gpios = <&gpio 34 GPIO_ACTIVE_LOW>;
		};
	};
};

Fallback to mdiobus_register() if no mdio-bus child node exists. This
way we don't need to touch all xway dts files, for which we don't know
the actual address on the mdio bus.

Signed-off-by: Johann Neuhauser <johann@it-neuhauser.de>

target/linux/lantiq/patches-4.14/0701-NET-lantiq-etop-of-mido.patch

@@ -0,0 +1,37 @@
+--- a/drivers/net/ethernet/lantiq_etop.c
++++ b/drivers/net/ethernet/lantiq_etop.c
+@@ -40,6 +40,7 @@
+ #include <linux/of_net.h>
+ #include <linux/of_irq.h>
+ #include <linux/of_platform.h>
++#include <linux/of_mdio.h>
+ 
+ #include <asm/checksum.h>
+ 
+@@ -567,7 +568,8 @@ static int
+ ltq_etop_mdio_init(struct net_device *dev)
+ {
+ 	struct ltq_etop_priv *priv = netdev_priv(dev);
+-	int err;
++	struct device_node *mdio_np = NULL;
++	int err, ret;
+ 
+ 	priv->mii_bus = mdiobus_alloc();
+ 	if (!priv->mii_bus) {
+@@ -587,7 +589,15 @@ ltq_etop_mdio_init(struct net_device *de
+ 	priv->mii_bus->name = "ltq_mii";
+ 	snprintf(priv->mii_bus->id, MII_BUS_ID_SIZE, "%s-%x",
+ 		priv->pdev->name, priv->pdev->id);
+-	if (mdiobus_register(priv->mii_bus)) {
++
++	mdio_np = of_get_child_by_name(priv->pdev->dev.of_node, "mdio-bus");
++
++	if (mdio_np)
++		ret = of_mdiobus_register(priv->mii_bus, mdio_np);
++	else
++		ret = mdiobus_register(priv->mii_bus);
++
++	if (ret) {
+ 		err = -ENXIO;
+ 		goto err_out_free_mdiobus;
+ 	}