Devicetree

mdio {
    #address-cells = <1>;
    #size-cells = <0>;
    phy: ethernet-phy@0 {
        ......
    };
    gmiitorgmii: gmiitorgmii@8 {
        compatible = "xlnx,gmii-to-rgmii-1.0";
        reg = <8>;
        phy-handle = <&phy>;
    };
};