dt-bindings: pwm: pwm-tiecap: Convert to json schema

Convert the tiecap binding to DT schema format using json-schema.
Along with this conversion the following changes are included:
- 'clock' and 'clock-names' properties are marked required as
   driver fails to probe without these properties
- Dropped ti,am33xx-ecap as it is no longer applicable.
- 'power-domains' property is introduced and marked as optional.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/pwm-tiecap.yaml

@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/pwm-tiecap.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI SOC ECAP based APWM controller
+
+maintainers:
+  - Vignesh R <vigneshr@ti.com>
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    oneOf:
+      - const: ti,am3352-ecap
+      - items:
+          - enum:
+              - ti,da850-ecap
+              - ti,am4372-ecap
+              - ti,dra746-ecap
+              - ti,k2g-ecap
+              - ti,am654-ecap
+          - const: ti,am3352-ecap
+
+  reg:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 3
+    description: |
+      See pwm.yaml in this directory for a description of the cells format.
+      The only third cell flag supported by this binding is PWM_POLARITY_INVERTED.
+
+  clock-names:
+    const: fck
+
+  clocks:
+    maxItems: 1
+
+  power-domains:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - "#pwm-cells"
+  - clocks
+  - clock-names
+
+additionalProperties: false
+
+examples:
+  - |
+    ecap0: pwm@48300100 { /* ECAP on am33xx */
+        compatible = "ti,am3352-ecap";
+        #pwm-cells = <3>;
+        reg = <0x48300100 0x80>;
+        clocks = <&l4ls_gclk>;
+        clock-names = "fck";
+    };