PHY nodes

If the device tree is used to describe networking interfaces, U-Boot expects a
node for each PHY.  Parent node for such a PHY node is expected to correspond to
a MDIO bus and the bus is used to access the PHY.

Required properties:

 - reg : The ID number for the phy, usually a small integer

Example:

ethernet-phy@0 {
	compatible = "ethernet-phy-id0141.0e90", "ethernet-phy-ieee802.3-c22";
	interrupt-parent = <&PIC>;
	interrupts = <35 IRQ_TYPE_EDGE_RISING>;
	reg = <0>;

	resets = <&rst 8>;
	reset-names = "phy";
	reset-gpios = <&gpio1 4 GPIO_ACTIVE_LOW>;
	reset-assert-us = <1000>;
	reset-deassert-us = <2000>;
};