Hisilicon MDIO bus controller

Properties:
- compatible: can be one of:
	"hisilicon,hns-mdio"
	"hisilicon,mdio"
  "hisilicon,hns-mdio" is recommended to be used for hip05 and later SOCs,
  while "hisilicon,mdio" is optional for backwards compatibility only on
  hip04 Soc.
- 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@803c0000 {
                   #address-cells = <1>;
                   #size-cells = <0>;
                   compatible = "hisilicon,hns-mdio","hisilicon,mdio";
                   reg = <0x0 0x803c0000 0x0 0x10000>;

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