[PATCH v2] dt-bindings: arm: cpus: Document pu-supply

[Fabio Estevam <festevam@gmail.com>]

The i.MX6Q Reference Manual describes the three digital LDO regulators
as follows:

"10.4.1.1.1
Digital LDO Regulators
The integrated PMU includes three digital LDO regulators: LDO_ARM, LDO_PU, and
LDO_SOC. These regulators provide power to the ARM_Core power domain, the
combined VPU, IPU and GPU power domain, and the rest of the SoC logic (except
always-ON SNVS domain)."

imx6dl.dtsi uses the correct names to describe these supplies:

arm-supply = <&reg_arm>;
pu-supply = <&reg_pu>;
soc-supply = <&reg_soc>;

'arm-supply' and 'soc-supply' are already documented, but 'pu-supply' is not.

Document the 'pu-supply' property and set it to deprecated.
    
This fixes the following dt-schema warning:
 
cpu@1 (arm,cortex-a9): Unevaluated properties are not allowed ('pu-supply' was unexpected)

Signed-off-by: Fabio Estevam <festevam@gmail.com>
---
Changes since v1:
- Explain that PU is a valid name. (Krzysztof)

 Documentation/devicetree/bindings/arm/cpus.yaml | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/cpus.yaml b/Documentation/devicetree/bindings/arm/cpus.yaml
index 4f1906d9fa68..c8a72fd02530 100644
--- a/Documentation/devicetree/bindings/arm/cpus.yaml
+++ b/Documentation/devicetree/bindings/arm/cpus.yaml
@@ -350,6 +350,10 @@ properties:
     deprecated: true
     description: Use 'cpu-supply' instead
 
+  pu-supply:
+    deprecated: true
+    description: Only for i.MX6Q/DL/SL SoCs.
+
   soc-supply:
     deprecated: true
     description: Only for i.MX6/7 Soc.
-- 
2.34.1