dt-bindings: clk: document PolarFire SoC fabric clocks

On PolarFire SoC there are 4 PLL/DLL blocks, located in each of the
ordinal corners of the chip, which our documentation refers to as
"Clock Conditioning Circuitry". PolarFire SoC is an FPGA, these are
highly configurable & many of the input clocks are optional.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220908143651.1252601-3-conor.dooley@microchip.com

diff --git a/Documentation/devicetree/bindings/clock/microchip,mpfs-ccc.yaml b/Documentation/devicetree/bindings/clock/microchip,mpfs-ccc.yaml
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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/microchip,mpfs-ccc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip PolarFire SoC Fabric Clock Conditioning Circuitry
+
+maintainers:
+  - Conor Dooley <conor.dooley@microchip.com>
+
+description: |
+  Microchip PolarFire SoC has 4 Clock Conditioning Circuitry blocks. Each of
+  these blocks contains two PLLs and 2 DLLs & are located in the four corners of
+  the FPGA. For more information see "PolarFire SoC FPGA Clocking Resources" at:
+  https://onlinedocs.microchip.com/pr/GUID-8F0CC4C0-0317-4262-89CA-CE7773ED1931-en-US-1/index.html
+
+properties:
+  compatible:
+    const: microchip,mpfs-ccc
+
+  reg:
+    items:
+      - description: PLL0's control registers
+      - description: PLL1's control registers
+      - description: DLL0's control registers
+      - description: DLL1's control registers
+
+  clocks:
+    description:
+      The CCC PLL's have two input clocks. It is required that even if the input
+      clocks are identical that both are provided.
+    minItems: 2
+    items:
+      - description: PLL0's refclk0
+      - description: PLL0's refclk1
+      - description: PLL1's refclk0
+      - description: PLL1's refclk1
+      - description: DLL0's refclk
+      - description: DLL1's refclk
+
+  clock-names:
+    minItems: 2
+    items:
+      - const: pll0_ref0
+      - const: pll0_ref1
+      - const: pll1_ref0
+      - const: pll1_ref1
+      - const: dll0_ref
+      - const: dll1_ref
+
+  '#clock-cells':
+    const: 1
+    description: |
+      The clock consumer should specify the desired clock by having the clock
+      ID in its "clocks" phandle cell.
+      See include/dt-bindings/clock/microchip,mpfs-clock.h for the full list of
+      PolarFire clock IDs.
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - '#clock-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    clock-controller@38100000 {
+        compatible = "microchip,mpfs-ccc";
+        reg = <0x38010000 0x1000>, <0x38020000 0x1000>,
+              <0x39010000 0x1000>, <0x39020000 0x1000>;
+        #clock-cells = <1>;
+        clocks = <&refclk_ccc>, <&refclk_ccc>, <&refclk_ccc>, <&refclk_ccc>,
+                  <&refclk_ccc>, <&refclk_ccc>;
+        clock-names = "pll0_ref0", "pll0_ref1", "pll1_ref0", "pll1_ref1",
+                      "dll0_ref", "dll1_ref";
+    };