Hisilicon MDIO bus controller

Properties:
- compatible: "hisilicon,mdio","hisilicon,hns-mdio".
- 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,mdio","hisilicon,hns-mdio";
                   reg = <0x0 0x803c0000 0x0 0x10000>;

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