Merge branch 'add-ast2400-2500-phy-handle-support'

Ivan Mikhaylov says:

====================
add ast2400/2500 phy-handle support

This patch introduces ast2400/2500 phy-handle support with an embedded
MDIO controller. At the current moment it is not possible to set options
with this format on ast2400/2500:

mac {
	phy-handle = <&phy>;
	phy-mode = "rgmii";

	mdio {
		#address-cells = <1>;
		#size-cells = <0>;

		phy: ethernet-phy@0 {
			compatible = "ethernet-phy-idxxxx.yyyy";
			reg = <0>;
		};
	};
};

The patch fixes it and gets possible PHYs and register them with
of_mdiobus_register.

Changes from v3:
   1. add dt-bindings description of MDIO node and phy-handle option
      with example.

Changes from v2:
   1. change manual phy interface type check on phy_interface_mode_is_rgmii
      function.
   2. add err_phy_connect label.
   3. split ftgmac100_destroy_mdio into ftgmac100_phy_disconnect and
      ftgmac100_destroy_mdio.
   4. remove unneeded mdio_np checks.

Changes from v1:
   1. split one patch into two.
====================

Link: https://lore.kernel.org/r/20201030133707.12099-1-i.mikhaylov@yadro.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>