SMSC LAN87xx Ethernet PHY

Some boards require special tuning values. Configure them
through an Ethernet OF device node.

Optional properties:

- clocks:
  The clock used as phy reference clock and is connected to phy
  pin XTAL1/CLKIN.

- smsc,disable-energy-detect:
  If set, do not enable energy detect mode for the SMSC phy.
  default: enable energy detect mode

Examples:
smsc phy with disabled energy detect mode on an am335x based board.
&davinci_mdio {
	pinctrl-names = "default", "sleep";
	pinctrl-0 = <&davinci_mdio_default>;
	pinctrl-1 = <&davinci_mdio_sleep>;

	ethernetphy0: ethernet-phy@0 {
		reg = <0>;
		smsc,disable-energy-detect;
	};
};