* Generic PM domains

System on chip designs are often divided into multiple PM domains that can be
used for power gating of selected IP blocks for power saving by reduced leakage
current.

This device tree binding can be used to bind PM domain consumer devices with
their PM domains provided by PM domain providers. A PM domain provider can be
represented by any node in the device tree and can provide one or more PM
domains. A consumer node can refer to the provider by a phandle and a set of
phandle arguments (so called PM domain specifiers) of length specified by the
#power-domain-cells property in the PM domain provider node.

==PM domain providers==

Required properties:
 - #power-domain-cells : Number of cells in a PM domain specifier;
   Typically 0 for nodes representing a single PM domain and 1 for nodes
   providing multiple PM domains (e.g. power controllers), but can be any value
   as specified by device tree binding documentation of particular provider.

Example:

	power: power-controller@12340000 {
		compatible = "foo,power-controller";
		reg = <0x12340000 0x1000>;
		#power-domain-cells = <1>;
	};

The node above defines a power controller that is a PM domain provider and
expects one cell as its phandle argument.

==PM domain consumers==

Required properties:
 - power-domains : A phandle and PM domain specifier as defined by bindings of
                   the power controller specified by phandle.

Example:

	leaky-device@12350000 {
		compatible = "foo,i-leak-current";
		reg = <0x12350000 0x1000>;
		power-domains = <&power 0>;
	};

The node above defines a typical PM domain consumer device, which is located
inside a PM domain with index 0 of a power controller represented by a node
with the label "power".