dt-bindings: pwm: Add bindings for OpenCores PWM Controller

Add bindings for OpenCores PWM Controller.
Signed-off-by: William Qiu <william.qiu@starfivetech.com>
Reviewed-by: Hal Feng <hal.feng@starfivetech.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

Documentation/devicetree/bindings/pwm/opencores,pwm.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/opencores,pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: OpenCores PWM controller
+
+maintainers:
+  - William Qiu <william.qiu@starfivetech.com>
+
+description:
+  The OpenCores PTC ip core contains a PWM controller. When operating in PWM
+  mode, the PTC core generates binary signal with user-programmable low and
+  high periods. All PTC counters and registers are 32-bit.
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - starfive,jh7100-pwm
+          - starfive,jh7110-pwm
+      - const: opencores,pwm-v1
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  resets:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 3
+
+required:
+  - compatible
+  - reg
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm@12490000 {
+        compatible = "starfive,jh7110-pwm", "opencores,pwm-v1";
+        reg = <0x12490000 0x10000>;
+        clocks = <&clkgen 181>;
+        resets = <&rstgen 109>;
+        #pwm-cells = <3>;
+    };