dt-bindings: riscv: convert pwm bindings to json-schema

Convert device tree bindings for SiFive's PWM controller to YAML
format.
Signed-off-by: Sagar Kadam <sagar.kadam@sifive.com>
Link: https://lore.kernel.org/r/1601393531-2402-4-git-send-email-sagar.kadam@sifive.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pwm/pwm-sifive.txt

-SiFive PWM controller
-
-Unlike most other PWM controllers, the SiFive PWM controller currently only
-supports one period for all channels in the PWM. All PWMs need to run at
-the same period. The period also has significant restrictions on the values
-it can achieve, which the driver rounds to the nearest achievable period.
-PWM RTL that corresponds to the IP block version numbers can be found
-here:
-
-https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/pwm
-
-Required properties:
-- compatible: Should be "sifive,<chip>-pwm" and "sifive,pwm<version>".
-  Supported compatible strings are: "sifive,fu540-c000-pwm" for the SiFive
-  PWM v0 as integrated onto the SiFive FU540 chip, and "sifive,pwm0" for the
-  SiFive PWM v0 IP block with no chip integration tweaks.
-  Please refer to sifive-blocks-ip-versioning.txt for details.
-- reg: physical base address and length of the controller's registers
-- clocks: Should contain a clock identifier for the PWM's parent clock.
-- #pwm-cells: Should be 3. See pwm.yaml in this directory
-  for a description of the cell format.
-- interrupts: one interrupt per PWM channel
-
-Examples:
-
-pwm:  pwm@10020000 {
-	compatible = "sifive,fu540-c000-pwm", "sifive,pwm0";
-	reg = <0x0 0x10020000 0x0 0x1000>;
-	clocks = <&tlclk>;
-	interrupt-parent = <&plic>;
-	interrupts = <42 43 44 45>;
-	#pwm-cells = <3>;
-};

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

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2020 SiFive, Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/pwm-sifive.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SiFive PWM controller
+
+maintainers:
+  - Yash Shah <yash.shah@sifive.com>
+  - Sagar Kadam <sagar.kadam@sifive.com>
+  - Paul Walmsley <paul.walmsley@sifive.com>
+
+description:
+  Unlike most other PWM controllers, the SiFive PWM controller currently
+  only supports one period for all channels in the PWM. All PWMs need to
+  run at the same period. The period also has significant restrictions on
+  the values it can achieve, which the driver rounds to the nearest
+  achievable period. PWM RTL that corresponds to the IP block version
+  numbers can be found here -
+
+  https://github.com/sifive/sifive-blocks/tree/master/src/main/scala/devices/pwm
+
+properties:
+  compatible:
+    items:
+      - const: sifive,fu540-c000-pwm
+      - const: sifive,pwm0
+    description:
+      Should be "sifive,<chip>-pwm" and "sifive,pwm<version>". Supported
+      compatible strings are "sifive,fu540-c000-pwm" for the SiFive PWM v0
+      as integrated onto the SiFive FU540 chip, and "sifive,pwm0" for the
+      SiFive PWM v0 IP block with no chip integration tweaks.
+      Please refer to sifive-blocks-ip-versioning.txt for details.
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 3
+
+  interrupts:
+    maxItems: 4
+    description:
+      Each PWM instance in FU540-C000 has 4 comparators. One interrupt per comparator.
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - "#pwm-cells"
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    pwm:  pwm@10020000 {
+      compatible = "sifive,fu540-c000-pwm", "sifive,pwm0";
+      reg = <0x10020000 0x1000>;
+      clocks = <&tlclk>;
+      interrupt-parent = <&plic>;
+      interrupts = <42>, <43>, <44>, <45>;
+      #pwm-cells = <3>;
+    };