dt-bindings: pwm: airoha: Add EN7581 pwm

Introduce device-tree binding documentation for Airoha EN7581 pwm
controller.

Co-developed-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Acked-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/20241023-en7581-pinctrl-v9-3-afb0cbcab0ec@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pwm/airoha,en7581-pwm.yaml

@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/airoha,en7581-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Airoha EN7581 PWM Controller
+
+maintainers:
+  - Lorenzo Bianconi <lorenzo@kernel.org>
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    const: airoha,en7581-pwm
+
+  "#pwm-cells":
+    const: 3
+
+required:
+  - compatible
+  - "#pwm-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm {
+      compatible = "airoha,en7581-pwm";
+
+      #pwm-cells = <3>;
+    };