* ARM Versatile Express Serial Power Controller device tree bindings

Latest ARM development boards implement a power management interface (serial
power controller - SPC) that is capable of managing power/voltage and
operating point transitions, through memory mapped registers interface.

On testchips like TC2 it also provides a configuration interface that can
be used to read/write values which cannot be read/written through simple
memory mapped reads/writes.

- spc node

	- compatible:
		Usage: required
		Value type: <stringlist>
		Definition: must be
			    "arm,vexpress-spc,v2p-ca15_a7","arm,vexpress-spc"
	- reg:
		Usage: required
		Value type: <prop-encode-array>
		Definition: A standard property that specifies the base address
			    and the size of the SPC address space
	- interrupts:
		Usage: required
		Value type: <prop-encoded-array>
		Definition:  SPC interrupt configuration. A standard property
			     that follows ePAPR interrupts specifications

Example:

spc: spc@7fff0000 {
	compatible = "arm,vexpress-spc,v2p-ca15_a7","arm,vexpress-spc";
	reg = <0 0x7FFF0000 0 0x1000>;
	interrupts = <0 95 4>;
};