dt-bindings: clock: Add Google gs101 clock management unit bindings

Provide dt-schema documentation for Google gs101 SoC clock controller.
Currently this adds support for cmu_top, cmu_misc and cmu_apm.
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231209233106.147416-3-peter.griffin@linaro.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Documentation/devicetree/bindings/clock/google,gs101-clock.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/google,gs101-clock.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Google GS101 SoC clock controller
+
+maintainers:
+  - Peter Griffin <peter.griffin@linaro.org>
+
+description: |
+  Google GS101 clock controller is comprised of several CMU units, generating
+  clocks for different domains. Those CMU units are modeled as separate device
+  tree nodes, and might depend on each other. The root clock in that clock tree
+  is OSCCLK (24.576 MHz). That external clock must be defined as a fixed-rate
+  clock in dts.
+
+  CMU_TOP is a top-level CMU, where all base clocks are prepared using PLLs and
+  dividers; all other leaf clocks (other CMUs) are usually derived from CMU_TOP.
+
+  Each clock is assigned an identifier and client nodes can use this identifier
+  to specify the clock which they consume. All clocks available for usage
+  in clock consumer nodes are defined as preprocessor macros in
+  'dt-bindings/clock/gs101.h' header.
+
+properties:
+  compatible:
+    enum:
+      - google,gs101-cmu-top
+      - google,gs101-cmu-apm
+      - google,gs101-cmu-misc
+
+  clocks:
+    minItems: 1
+    maxItems: 2
+
+  clock-names:
+    minItems: 1
+    maxItems: 2
+
+  "#clock-cells":
+    const: 1
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - "#clock-cells"
+  - clocks
+  - clock-names
+  - reg
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - google,gs101-cmu-top
+              - google,gs101-cmu-apm
+    then:
+      properties:
+        clocks:
+          items:
+            - description: External reference clock (24.576 MHz)
+
+        clock-names:
+          items:
+            - const: oscclk
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: google,gs101-cmu-misc
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: Misc bus clock (from CMU_TOP)
+            - description: Misc sss clock (from CMU_TOP)
+
+        clock-names:
+          items:
+            - const: dout_cmu_misc_bus
+            - const: dout_cmu_misc_sss
+
+additionalProperties: false
+
+examples:
+  # Clock controller node for CMU_TOP
+  - |
+    #include <dt-bindings/clock/google,gs101.h>
+
+    cmu_top: clock-controller@1e080000 {
+        compatible = "google,gs101-cmu-top";
+        reg = <0x1e080000 0x8000>;
+        #clock-cells = <1>;
+        clocks = <&ext_24_5m>;
+        clock-names = "oscclk";
+    };
+
+...