dt-bindings: timer: nuvoton,npcm7xx-timer: Convert to YAML

Let's convert this devicetree binding to YAML, to make it easier to
extend later.
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220130102704.2892072-1-j.neuschaefer@gmx.net

Documentation/devicetree/bindings/timer/nuvoton,npcm7xx-timer.txt

-Nuvoton NPCM7xx timer
-
-Nuvoton NPCM7xx have three timer modules, each timer module provides five 24-bit
-timer counters.
-
-Required properties:
-- compatible      : "nuvoton,npcm750-timer" for Poleg NPCM750, or
-                    "nuvoton,wpcm450-timer" for Hermon WPCM450.
-- reg             : Offset and length of the register set for the device.
-- interrupts      : Contain the timer interrupt of timer 0.
-- clocks          : phandle of timer reference clock (usually a 25 MHz clock).
-
-Example:
-
-timer@f0008000 {
-    compatible = "nuvoton,npcm750-timer";
-    interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
-    reg = <0xf0008000 0x50>;
-    clocks = <&clk NPCM7XX_CLK_TIMER>;
-};
-

Documentation/devicetree/bindings/timer/nuvoton,npcm7xx-timer.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/nuvoton,npcm7xx-timer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Nuvoton NPCM7xx timer
+
+maintainers:
+  - Jonathan Neuschäfer <j.neuschaefer@gmx.net>
+
+properties:
+  compatible:
+    enum:
+      - nuvoton,wpcm450-timer  # for Hermon WPCM450
+      - nuvoton,npcm750-timer  # for Poleg NPCM750
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: The timer interrupt of timer 0
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/nuvoton,npcm7xx-clock.h>
+    timer@f0008000 {
+        compatible = "nuvoton,npcm750-timer";
+        interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
+        reg = <0xf0008000 0x50>;
+        clocks = <&clk NPCM7XX_CLK_TIMER>;
+    };