* System Management Interface (SMI) / MDIO

Properties:
- compatible: One of:

   "cavium,octeon-3860-mdio": Compatibility with all cn3XXX, cn5XXX
                       and cn6XXX SOCs.

   "cavium,thunder-8890-mdio": Compatibility with all cn8XXX SOCs.

- reg: The base address of the MDIO bus controller register bank.

- #address-cells: Must be <1>.

- #size-cells: Must be <0>.  MDIO addresses have no size component.

Typically an MDIO bus might have several children.

Example:
	mdio@1180000001800 {
		compatible = "cavium,octeon-3860-mdio";
		#address-cells = <1>;
		#size-cells = <0>;
		reg = <0x11800 0x00001800 0x0 0x40>;

		ethernet-phy@0 {
			...
			reg = <0>;
		};
	};


* System Management Interface (SMI) / MDIO Nexus

  Several mdio buses may be gathered as children of a single PCI
  device, this PCI device is the nexus of the buses.

Properties:

- compatible: "cavium,thunder-8890-mdio-nexus";

- reg: The PCI device and function numbers of the nexus device.

- #address-cells: Must be <2>.

- #size-cells: Must be <2>.

- ranges: As needed for mapping of the MDIO bus device registers.

- assigned-addresses: As needed for mapping of the MDIO bus device registers.

Example:

        mdio-nexus@1,3 {
                compatible = "cavium,thunder-8890-mdio-nexus";
                #address-cells = <2>;
                #size-cells = <2>;
                reg = <0x0b00 0 0 0 0>; /* DEVFN = 0x0b (1:3) */
                assigned-addresses = <0x03000000 0x87e0 0x05000000 0x0 0x800000>;
                ranges = <0x87e0 0x05000000 0x03000000 0x87e0 0x05000000 0x0 0x800000>;

                mdio0@87e0,05003800 {
                        compatible = "cavium,thunder-8890-mdio";
                        #address-cells = <1>;
                        #size-cells = <0>;
                        reg = <0x87e0 0x05003800 0x0 0x30>;

                        ethernet-phy@0 {
                                ...
                                reg = <0>;
                        };
                };
                mdio0@87e0,05003880 {
                        compatible = "cavium,thunder-8890-mdio";
                        #address-cells = <1>;
                        #size-cells = <0>;
                        reg = <0x87e0 0x05003880 0x0 0x30>;

                        ethernet-phy@0 {
                                ...
                                reg = <0>;
                        };
                };
        };