PHY nodes

Required properties:

 - interrupts : <a b> where a is the interrupt number and b is a
   field that represents an encoding of the sense and level
   information for the interrupt.  This should be encoded based on
   the information in section 2) depending on the type of interrupt
   controller you have.
 - interrupt-parent : the phandle for the interrupt controller that
   services interrupts for this device.
 - reg : The ID number for the phy, usually a small integer

Optional Properties:

- compatible: Compatible list, may contain
  "ethernet-phy-ieee802.3-c22" or "ethernet-phy-ieee802.3-c45" for
  PHYs that implement IEEE802.3 clause 22 or IEEE802.3 clause 45
  specifications. If neither of these are specified, the default is to
  assume clause 22. The compatible list may also contain other
  elements.

  If the phy's identifier is known then the list may contain an entry
  of the form: "ethernet-phy-idAAAA.BBBB" where
     AAAA - The value of the 16 bit Phy Identifier 1 register as
            4 hex digits. This is the chip vendor OUI bits 3:18
     BBBB - The value of the 16 bit Phy Identifier 2 register as
            4 hex digits. This is the chip vendor OUI bits 19:24,
            followed by 10 bits of a vendor specific ID.

- max-speed: Maximum PHY supported speed (10, 100, 1000...)

- broken-turn-around: If set, indicates the PHY device does not correctly
  release the turn around line low at the end of a MDIO transaction.

Example:

ethernet-phy@0 {
	compatible = "ethernet-phy-id0141.0e90", "ethernet-phy-ieee802.3-c22";
	interrupt-parent = <40000>;
	interrupts = <35 1>;
	reg = <0>;
};
