dt-bindings: clock: Document Exynos850 CMU bindings

Provide dt-schema documentation for Exynos850 SoC clock controller.
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Link: https://lore.kernel.org/r/20211008154352.19519-5-semen.protsenko@linaro.orgSigned-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

Documentation/devicetree/bindings/clock/samsung,exynos850-clock.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/samsung,exynos850-clock.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung Exynos850 SoC clock controller
+
+maintainers:
+  - Sam Protsenko <semen.protsenko@linaro.org>
+  - Chanwoo Choi <cw00.choi@samsung.com>
+  - Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
+  - Sylwester Nawrocki <s.nawrocki@samsung.com>
+  - Tomasz Figa <tomasz.figa@gmail.com>
+
+description: |
+  Exynos850 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. Root clocks in that clock tree are
+  two external clocks:: OSCCLK (26 MHz) and RTCCLK (32768 Hz). Those external
+  clocks must be defined as fixed-rate clocks 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/exynos850.h' header.
+
+properties:
+  compatible:
+    enum:
+      - samsung,exynos850-cmu-top
+      - samsung,exynos850-cmu-core
+      - samsung,exynos850-cmu-dpu
+      - samsung,exynos850-cmu-hsi
+      - samsung,exynos850-cmu-peri
+
+  clocks:
+    minItems: 1
+    maxItems: 5
+
+  clock-names:
+    minItems: 1
+    maxItems: 5
+
+  "#clock-cells":
+    const: 1
+
+  reg:
+    maxItems: 1
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos850-cmu-top
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: External reference clock (26 MHz)
+
+        clock-names:
+          items:
+            - const: oscclk
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos850-cmu-core
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: External reference clock (26 MHz)
+            - description: CMU_CORE bus clock (from CMU_TOP)
+            - description: CCI clock (from CMU_TOP)
+            - description: eMMC clock (from CMU_TOP)
+            - description: SSS clock (from CMU_TOP)
+
+        clock-names:
+          items:
+            - const: oscclk
+            - const: dout_core_bus
+            - const: dout_core_cci
+            - const: dout_core_mmc_embd
+            - const: dout_core_sss
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos850-cmu-dpu
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: External reference clock (26 MHz)
+            - description: DPU clock (from CMU_TOP)
+
+        clock-names:
+          items:
+            - const: oscclk
+            - const: dout_dpu
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos850-cmu-hsi
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: External reference clock (26 MHz)
+            - description: External RTC clock (32768 Hz)
+            - description: CMU_HSI bus clock (from CMU_TOP)
+            - description: SD card clock (from CMU_TOP)
+            - description: "USB 2.0 DRD clock (from CMU_TOP)"
+
+        clock-names:
+          items:
+            - const: oscclk
+            - const: rtcclk
+            - const: dout_hsi_bus
+            - const: dout_hsi_mmc_card
+            - const: dout_hsi_usb20drd
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos850-cmu-peri
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: External reference clock (26 MHz)
+            - description: CMU_PERI bus clock (from CMU_TOP)
+            - description: UART clock (from CMU_TOP)
+            - description: Parent clock for HSI2C and SPI (from CMU_TOP)
+
+        clock-names:
+          items:
+            - const: oscclk
+            - const: dout_peri_bus
+            - const: dout_peri_uart
+            - const: dout_peri_ip
+
+required:
+  - compatible
+  - "#clock-cells"
+  - clocks
+  - clock-names
+  - reg
+
+additionalProperties: false
+
+examples:
+  # Clock controller node for CMU_PERI
+  - |
+    #include <dt-bindings/clock/exynos850.h>
+
+    cmu_peri: clock-controller@10030000 {
+        compatible = "samsung,exynos850-cmu-peri";
+        reg = <0x10030000 0x8000>;
+        #clock-cells = <1>;
+
+        clocks = <&oscclk>, <&cmu_top CLK_DOUT_PERI_BUS>,
+                 <&cmu_top CLK_DOUT_PERI_UART>,
+                 <&cmu_top CLK_DOUT_PERI_IP>;
+        clock-names = "oscclk", "dout_peri_bus",
+                      "dout_peri_uart", "dout_peri_ip";
+    };
+
+...