* Synopsys ARC EMAC 10/100 Ethernet driver (EMAC)

Required properties:
- compatible: Should be "snps,arc-emac"
- reg: Address and length of the register set for the device
- interrupts: Should contain the EMAC interrupts
- max-speed: see ethernet.txt file in the same directory.
- phy: see ethernet.txt file in the same directory.

Optional properties:
- phy-reset-gpios : Should specify the gpio for phy reset
- phy-reset-duration : Reset duration in milliseconds.  Should present
  only if property "phy-reset-gpios" is available.  Missing the property
  will have the duration be 1 millisecond.  Numbers greater than 1000 are
  invalid and 1 millisecond will be used instead.

Clock handling:
The clock frequency is needed to calculate and set polling period of EMAC.
It must be provided by one of:
- clock-frequency: CPU frequency.
- clocks: reference to the clock supplying the EMAC.

Child nodes of the driver are the individual PHY devices connected to the
MDIO bus. They must have a "reg" property given the PHY address on the MDIO bus.

Examples:

	ethernet@c0fc2000 {
		compatible = "snps,arc-emac";
		reg = <0xc0fc2000 0x3c>;
		interrupts = <6>;
		mac-address = [ 00 11 22 33 44 55 ];

		clock-frequency = <80000000>;
		/* or */
		clocks = <&emac_clock>;

		max-speed = <100>;
		phy = <&phy0>;

		#address-cells = <1>;
		#size-cells = <0>;
		phy0: ethernet-phy@0 {
			reg = <1>;
		};
	};
