Documentation: devicetree: add Broadcom Starfighter 2 binding

* Broadcom Starfighter 2 integrated swich

Required properties:

- compatible: should be "brcm,bcm7445-switch-v4.0"

- reg: addresses and length of the register sets for the device, must be 6

  pairs of register addresses and lengths

- interrupts: interrupts for the devices, must be two interrupts

- dsa,mii-bus: phandle to the MDIO bus controller, see dsa/dsa.txt

- dsa,ethernet: phandle to the CPU network interface controller, see dsa/dsa.txt

- #size-cells: must be 0

- #address-cells: must be 2, see dsa/dsa.txt

Subnodes:

The integrated switch subnode should be specified according to the binding

described in dsa/dsa.txt.

Optional properties:

- reg-names: litteral names for the device base register addresses, when present

  must be: "core", "reg", "intrl2_0", "intrl2_1", "fcb", "acb"

- interrupt-names: litternal names for the device interrupt lines, when present

  must be: "switch_0" and "switch_1"

- brcm,num-gphy: specify the maximum number of integrated gigabit PHYs in the

  switch

- brcm,num-rgmii-ports: specify the maximum number of RGMII interfaces supported

  by the switch

- brcm,fcb-pause-override: boolean property, if present indicates that the switch

  supports Failover Control Block pause override capability

- brcm,acb-packets-inflight: boolean property, if present indicates that the switch

  Admission Control Block supports reporting the number of packets in-flight in a

  switch queue

Example:

switch_top@f0b00000 {

	compatible = "simple-bus";

	#size-cells = <1>;

	#address-cells = <1>;

	ranges = <0 0xf0b00000 0x40804>;

	ethernet_switch@0 {

		compatible = "brcm,bcm7445-switch-v4.0";

		#size-cells = <0>;

		#address-cells = <2>;

		reg = <0x0 0x40000

			0x40000 0x110

			0x40340 0x30

			0x40380 0x30

			0x40400 0x34

			0x40600 0x208>;

		interrupts = <0 0x18 0

				0 0x19 0>;

		brcm,num-gphy = <1>;

		brcm,num-rgmii-ports = <2>;

		brcm,fcb-pause-override;

		brcm,acb-packets-inflight;

		...

		switch@0 {

			reg = <0 0>;

			#size-cells = <0>;

			#address-cells <1>;

			port@0 {

				label = "gphy";

				reg = <0>;

			};

			...

		};

	};

};