dt-bindings: power: Convert domain-idle-states bindings to json-schema

While converting to the json-schema, let's also take the opportunity to
further specify/clarify some more details about the DT binding.

For example, let's define the label where to put the states nodes, set a
pattern for nodename of the state nodes and finally add an example.

Fixes: a3f048b5424e ("dt: psci: Update DT bindings to support hierarchical PSCI states")
Signed-off-by: Ulf Hansson <[e-mail]>
[robh: drop type refs from standard unit properties]
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/arm/psci.yaml

···
       to mandate it.
 
       [3] Documentation/devicetree/bindings/power/power_domain.txt
-      [4] Documentation/devicetree/bindings/power/domain-idle-state.txt
+      [4] Documentation/devicetree/bindings/power/domain-idle-state.yaml
 
   power-domains:
     $ref: '/schemas/types.yaml#/definitions/phandle-array'

Documentation/devicetree/bindings/power/domain-idle-state.txt

···
-PM Domain Idle State Node:
-
-A domain idle state node represents the state parameters that will be used to
-select the state when there are no active components in the domain.
-
-The state node has the following parameters -
-
-- compatible:
-	Usage: Required
-	Value type: <string>
-	Definition: Must be "domain-idle-state".
-
-- entry-latency-us
-	Usage: Required
-	Value type: <prop-encoded-array>
-	Definition: u32 value representing worst case latency in
-		    microseconds required to enter the idle state.
-		    The exit-latency-us duration may be guaranteed
-		    only after entry-latency-us has passed.
-
-- exit-latency-us
-	Usage: Required
-	Value type: <prop-encoded-array>
-	Definition: u32 value representing worst case latency
-		    in microseconds required to exit the idle state.
-
-- min-residency-us
-	Usage: Required
-	Value type: <prop-encoded-array>
-	Definition: u32 value representing minimum residency duration
-		    in microseconds after which the idle state will yield
-		    power benefits after overcoming the overhead in entering
-i		    the idle state.

Documentation/devicetree/bindings/power/domain-idle-state.yaml

···
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/domain-idle-state.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: PM Domain Idle States binding description
+
+maintainers:
+  - Ulf Hansson <[e-mail]>
+
+description:
+  A domain idle state node represents the state parameters that will be used to
+  select the state when there are no active components in the PM domain.
+
+properties:
+  $nodename:
+    const: domain-idle-states
+
+patternProperties:
+  "^(cpu|cluster|domain)-":
+    type: object
+    description:
+      Each state node represents a domain idle state description.
+
+    properties:
+      compatible:
+        const: domain-idle-state
+
+      entry-latency-us:
+        description:
+          The worst case latency in microseconds required to enter the idle
+          state. Note that, the exit-latency-us duration may be guaranteed only
+          after the entry-latency-us has passed.
+
+      exit-latency-us:
+        description:
+          The worst case latency in microseconds required to exit the idle
+          state.
+
+      min-residency-us:
+        description:
+          The minimum residency duration in microseconds after which the idle
+          state will yield power benefits, after overcoming the overhead while
+          entering the idle state.
+
+    required:
+      - compatible
+      - entry-latency-us
+      - exit-latency-us
+      - min-residency-us
+
+examples:
+  - |
+
+    domain-idle-states {
+      domain_retention: domain-retention {
+        compatible = "domain-idle-state";
+        entry-latency-us = <20>;
+        exit-latency-us = <40>;
+        min-residency-us = <80>;
+      };
+    };
+...

Documentation/devicetree/bindings/power/power-domain.yaml

···
 
   domain-idle-states:
     $ref: /schemas/types.yaml#/definitions/phandle-array
-    description:
-      A phandle of an idle-state that shall be soaked into a generic domain
-      power state. The idle state definitions are compatible with
-      domain-idle-state specified in
-      Documentation/devicetree/bindings/power/domain-idle-state.txt
-      phandles that are not compatible with domain-idle-state will be ignored.
-      The domain-idle-state property reflects the idle state of this PM domain
-      and not the idle states of the devices or sub-domains in the PM domain.
-      Devices and sub-domains have their own idle-states independent
-      of the parent domain's idle states. In the absence of this property,
-      the domain would be considered as capable of being powered-on
-      or powered-off.
+    description: |
+      Phandles of idle states that defines the available states for the
+      power-domain provider. The idle state definitions are compatible with the
+      domain-idle-state bindings, specified in ./domain-idle-state.yaml.
+
+      Note that, the domain-idle-state property reflects the idle states of this
+      PM domain and not the idle states of the devices or sub-domains in the PM
+      domain. Devices and sub-domains have their own idle states independent of
+      the parent domain's idle states. In the absence of this property, the
+      domain would be considered as capable of being powered-on or powered-off.
 
   operating-points-v2:
     $ref: /schemas/types.yaml#/definitions/phandle-array

Documentation/devicetree/bindings/power/power_domain.txt

···
 		required-opps = <&domain1_opp_1>;
 	};
 
-[1]. Documentation/devicetree/bindings/power/domain-idle-state.txt
+[1]. Documentation/devicetree/bindings/power/domain-idle-state.yaml