quoted

If you want to describe the MDIO controller, then you embed a mdio
subnode into your Ethernet MAC node:

 emac0: ethernet@feb20000 {
	mdio {
		#address-cells = <1>;
		#size-cells = <0>;

		phy0: ethernet-phy@0 {
			reg = <0>;
		};
	};
};

And then each Ethernet MAC controller refers to their appropriate PHY
device tree node using a phy-handle property to point to either their
own MDIO controller, or another MAC's MDIO controller.

Sorry, I do not understand how phy-handle point to MDIO controller,
because phy-handle is defined to point to a phy.

The MAC driver does not care what MDIO controller a PHY is on. All you
need to do to register the PHY is:

	phy_node = of_parse_phandle(np, "phy-handle", 0);
	phy_interface = of_get_phy_mode(np);
	phydev = of_phy_connect(dev, phy_node,
                                &handle_link_change, 0,
                                phy_interface);

	Andrew