dt-bindings: serial: actions,owl-uart: convert to dtschema

Convert the Actions Semi Owl UART to newer DT schema.
Created DT schema based on the .txt file which had
`compatible`, `reg` and `interrupts` as the
required properties. This binding is used by Actions S500, S700
and S900 SoC. S700 and S900 use the same UART compatible string.

Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Kanak Shilledar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/serial/actions,owl-uart.txt

···
-Actions Semi Owl UART
-
-Required properties:
-- compatible :  "actions,s500-uart", "actions,owl-uart" for S500
-                "actions,s900-uart", "actions,owl-uart" for S900
-- reg        :  Offset and length of the register set for the device.
-- interrupts :  Should contain UART interrupt.
-
-
-Example:
-
-		uart3: serial@b0126000 {
-			compatible = "actions,s500-uart", "actions,owl-uart";
-			reg = <0xb0126000 0x1000>;
-			interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
-		};

Documentation/devicetree/bindings/serial/actions,owl-uart.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/actions,owl-uart.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Actions Semi Owl UART
+
+maintainers:
+  - Kanak Shilledar <[e-mail]>
+
+allOf:
+  - $ref: serial.yaml
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - actions,s500-uart
+          - actions,s900-uart
+      - const: actions,owl-uart
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/actions,s500-cmu.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    uart0: serial@b0126000 {
+        compatible = "actions,s500-uart", "actions,owl-uart";
+        reg = <0xb0126000 0x1000>;
+        clocks = <&cmu CLK_UART0>;
+        interrupts = <GIC_SPI 32 IRQ_TYPE_LEVEL_HIGH>;
+    };