dt-bindings: pwm: Convert BCM7038 PWM binding to YAML

Convert the Broadcom STB BCM7038 PWM Device Tree binding to YAML to help
with validation.
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20211208003727.3596577-4-f.fainelli@gmail.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.txt

-Broadcom BCM7038 PWM controller (BCM7xxx Set Top Box PWM controller)
-
-Required properties:
-
-- compatible: must be "brcm,bcm7038-pwm"
-- reg: physical base address and length for this controller
-- #pwm-cells: should be 2. See pwm.yaml in this directory for a description
-  of the cells format
-- clocks: a phandle to the reference clock for this block which is fed through
-  its internal variable clock frequency generator
-
-
-Example:
-
-	pwm: pwm@f0408000 {
-		compatible = "brcm,bcm7038-pwm";
-		reg = <0xf0408000 0x28>;
-		#pwm-cells = <2>;
-		clocks = <&upg_fixed>;
-	};

Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/brcm,bcm7038-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM7038 PWM controller (BCM7xxx Set Top Box PWM controller)
+
+maintainers:
+  - Florian Fainelli <f.fainelli@gmail.com>
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    const: brcm,bcm7038-pwm
+
+  reg:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 2
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - "#pwm-cells"
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm: pwm@f0408000 {
+       compatible = "brcm,bcm7038-pwm";
+       reg = <0xf0408000 0x28>;
+       #pwm-cells = <2>;
+       clocks = <&upg_fixed>;
+    };