dt-bindings: clock: renesas: Document RZ/G2L SoC CPG driver

Document the device tree bindings of the Renesas RZ/G2L SoC clock
driver in Documentation/devicetree/bindings/clock/renesas,rzg2l-cpg.yaml.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210609153230.6967-8-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/clock/renesas,rzg2l-cpg.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Renesas RZ/G2L Clock Pulse Generator / Module Standby Mode
+
+maintainers:
+  - Geert Uytterhoeven <geert+renesas@glider.be>
+
+description: |
+  On Renesas RZ/G2L SoC, the CPG (Clock Pulse Generator) and Module
+  Standby Mode share the same register block.
+
+  They provide the following functionalities:
+    - The CPG block generates various core clocks,
+    - The Module Standby Mode block provides two functions:
+        1. Module Standby, providing a Clock Domain to control the clock supply
+           to individual SoC devices,
+        2. Reset Control, to perform a software reset of individual SoC devices.
+
+properties:
+  compatible:
+    const: renesas,r9a07g044-cpg  # RZ/G2{L,LC}
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    description:
+      Clock source to CPG can be either from external clock input (EXCLK) or
+      crystal oscillator (XIN/XOUT).
+    const: extal
+
+  '#clock-cells':
+    description: |
+      - For CPG core clocks, the two clock specifier cells must be "CPG_CORE"
+        and a core clock reference, as defined in
+        <dt-bindings/clock/r9a07g044-cpg.h>
+      - For module clocks, the two clock specifier cells must be "CPG_MOD" and
+        a module number, as defined in the <dt-bindings/clock/r9a07g044-cpg.h>.
+    const: 2
+
+  '#power-domain-cells':
+    description:
+      SoC devices that are part of the CPG/Module Standby Mode Clock Domain and
+      can be power-managed through Module Standby should refer to the CPG device
+      node in their "power-domains" property, as documented by the generic PM
+      Domain bindings in Documentation/devicetree/bindings/power/power-domain.yaml.
+    const: 0
+
+  '#reset-cells':
+    description:
+      The single reset specifier cell must be the module number, as defined in
+      the <dt-bindings/clock/r9a07g044-cpg.h>.
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - '#clock-cells'
+  - '#power-domain-cells'
+  - '#reset-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    cpg: clock-controller@11010000 {
+            compatible = "renesas,r9a07g044-cpg";
+            reg = <0x11010000 0x10000>;
+            clocks = <&extal_clk>;
+            clock-names = "extal";
+            #clock-cells = <2>;
+            #power-domain-cells = <0>;
+            #reset-cells = <1>;
+    };