dt-bindings: clk: si521xx: Add Skyworks Si521xx I2C PCIe clock generators

Add binding for Skyworks Si521xx PCIe clock generators. This binding
is designed to support Si52144/Si52146/Si52147 series I2C PCIe clock
generators, tested model is Si52144. It should be possible to add
Si5213x series as well.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20230118191521.15544-1-marex@denx.deSigned-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/skyworks,si521xx.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/skyworks,si521xx.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Skyworks Si521xx I2C PCIe clock generators
+
+description: |
+  The Skyworks Si521xx are I2C PCIe clock generators providing
+  from 4 to 9 output clocks.
+
+maintainers:
+  - Marek Vasut <marex@denx.de>
+
+properties:
+  compatible:
+    enum:
+      - skyworks,si52144
+      - skyworks,si52146
+      - skyworks,si52147
+
+  reg:
+    const: 0x6b
+
+  '#clock-cells':
+    const: 1
+
+  clocks:
+    items:
+      - description: XTal input clock
+
+  skyworks,out-amplitude-microvolt:
+    enum: [ 300000, 400000, 500000, 600000, 700000, 800000, 900000, 1000000 ]
+    description: Output clock signal amplitude
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - '#clock-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        clock-generator@6b {
+            compatible = "skyworks,si52144";
+            reg = <0x6b>;
+            #clock-cells = <1>;
+            clocks = <&ref25m>;
+        };
+    };
+
+...