dt-bindings: pwm: sophgo: add PWM controller for SG2042

Sophgo SG2042 contains a PWM controller, which has 4 channels and
can generate PWM waveforms output.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Link: https://lore.kernel.org/r/d739ea5a1bffcf762248efbe25fae9b9fda6f452.1738737617.git.unicorn_wang@outlook.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

Author: unicornx

Documentation/devicetree/bindings/pwm/sophgo,sg2042-pwm.yaml

@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/sophgo,sg2042-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Sophgo SG2042 PWM controller
+
+maintainers:
+  - Chen Wang <unicorn_wang@outlook.com>
+
+description:
+  This controller contains 4 channels which can generate PWM waveforms.
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    const: sophgo,sg2042-pwm
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: apb
+
+  resets:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 3
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - resets
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/reset/sophgo,sg2042-reset.h>
+
+    pwm@7f006000 {
+        compatible = "sophgo,sg2042-pwm";
+        reg = <0x7f006000 0x1000>;
+        #pwm-cells = <3>;
+        clocks = <&clock 67>;
+        clock-names = "apb";
+        resets = <&rstgen RST_PWM>;
+    };