PM / Domains: dt: Allow power-domain property to be a list of specifiers

To be able to describe topologies where devices are partitioned across
multiple power domains, let's extend the power-domain property to allow
being a list of PM domain specifiers.
Suggested-by: NJon Hunter <jonathanh@nvidia.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/devicetree/bindings/power/power_domain.txt

@@ -111,8 +111,8 @@ Example 3:
 ==PM domain consumers==
 
 Required properties:
- - power-domains : A phandle and PM domain specifier as defined by bindings of
-                   the power controller specified by phandle.
+ - power-domains : A list of PM domain specifiers, as defined by bindings of
+		the power controller that is the PM domain provider.
 
 Example:
 
@@ -122,9 +122,18 @@ Example:
 		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".
+	leaky-device@12351000 {
+		compatible = "foo,i-leak-current";
+		reg = <0x12351000 0x1000>;
+		power-domains = <&power 0>, <&power 1> ;
+	};
+
+The first example 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".
+In the second example the consumer device are partitioned across two PM domains,
+the first with index 0 and the second with index 1, of a power controller that
+is represented by a node with the label "power.
 
 Optional properties:
 - required-opps: This contains phandle to an OPP node in another device's OPP