* 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
- clock-frequency: CPU frequency. It is needed to calculate and set polling
period of EMAC.
- max-speed: Maximum supported data-rate in Mbit/s. In some HW configurations
bandwidth of external memory controller might be a limiting factor. That's why
it's required to specify which data-rate is supported on current SoC or FPGA.
For example if only 10 Mbit/s is supported (10BASE-T) set "10". If 100 Mbit/s is
supported (100BASE-TX) set "100".
- phy: PHY device attached to the EMAC via MDIO bus

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.

Optional properties:
- mac-address: 6 bytes, mac address

Examples:

	ethernet@c0fc2000 {
		compatible = "snps,arc-emac";
		reg = <0xc0fc2000 0x3c>;
		interrupts = <6>;
		mac-address = [ 00 11 22 33 44 55 ];
		clock-frequency = <80000000>;
		max-speed = <100>;
		phy = <&phy0>;

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