ZHAW InES PTP time stamping IP core

The IP core needs two different kinds of nodes.  The control node
lives somewhere in the memory map and specifies the address of the
control registers.  There can be up to three port handles placed as
attributes of PHY nodes.  These associate a particular MII bus with a
port index within the IP core.

Required properties of the control node:

- compatible:		"ines,ptp-ctrl"
- reg:			physical address and size of the register bank

Required format of the port handle within the PHY node:

- timestamper:		provides control node reference and
			the port channel within the IP core

Example:

	tstamper: timestamper@60000000 {
		compatible = "ines,ptp-ctrl";
		reg = <0x60000000 0x80>;
	};

	ethernet@80000000 {
		...
		mdio {
			...
			ethernet-phy@3 {
				...
				timestamper = <&tstamper 0>;
			};
		};
	};