dt-bindings: serial: meson-uart: convert to yaml

Now that we have the DT validation in place, let's convert the device tree
bindings for the Amlogic UART Serial controller over to a YAML schemas.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/serial/amlogic,meson-uart.txt

-Amlogic Meson SoC UART Serial Interface
-=======================================
-
-The Amlogic Meson SoC UART Serial Interface is present on a large range
-of SoCs, and can be present either in the "Always-On" power domain or the
-"Everything-Else" power domain.
-
-The particularity of the "Always-On" Serial Interface is that the hardware
-is active since power-on and does not need any clock gating and is usable
-as very early serial console.
-
-Required properties:
-- compatible : compatible: value should be different for each SoC family as :
-	- Meson6 : "amlogic,meson6-uart"
-	- Meson8 : "amlogic,meson8-uart"
-	- Meson8b : "amlogic,meson8b-uart"
-	- GX (GXBB, GXL, GXM) : "amlogic,meson-gx-uart"
-	eventually followed by : "amlogic,meson-ao-uart" if this UART interface
-	is in the "Always-On" power domain.
-- reg : offset and length of the register set for the device.
-- interrupts : identifier to the device interrupt
-- clocks : a list of phandle + clock-specifier pairs, one for each
-	   entry in clock names.
-- clock-names :
-   * "xtal" for external xtal clock identifier
-   * "pclk" for the bus core clock, either the clk81 clock or the gate clock
-   * "baud" for the source of the baudrate generator, can be either the xtal
-	or the pclk.
-
-e.g.
-uart_A: serial@84c0 {
-	compatible = "amlogic,meson-gx-uart";
-	reg = <0x0 0x84c0 0x0 0x14>;
-	interrupts = <GIC_SPI 26 IRQ_TYPE_EDGE_RISING>;
-	/* Use xtal as baud rate clock source */
-	clocks = <&xtal>, <&clkc CLKID_UART0>, <&xtal>;
-	clock-names = "xtal", "pclk", "baud";
-};

Documentation/devicetree/bindings/serial/amlogic,meson-uart.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2019 BayLibre, SAS
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/serial/amlogic,meson-uart.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Amlogic Meson SoC UART Serial Interface
+
+maintainers:
+  - Neil Armstrong <narmstrong@baylibre.com>
+
+description: |
+  The Amlogic Meson SoC UART Serial Interface is present on a large range
+  of SoCs, and can be present either in the "Always-On" power domain or the
+  "Everything-Else" power domain.
+
+  The particularity of the "Always-On" Serial Interface is that the hardware
+  is active since power-on and does not need any clock gating and is usable
+  as very early serial console.
+
+properties:
+  compatible:
+    oneOf:
+      - description: Always-on power domain UART controller
+        items:
+        - enum:
+          - amlogic,meson6-uart
+          - amlogic,meson8-uart
+          - amlogic,meson8b-uart
+          - amlogic,meson-gx-uart
+        - const: amlogic,meson-ao-uart
+      - description: Everything-Else power domain UART controller
+        enum:
+        - amlogic,meson6-uart
+        - amlogic,meson8-uart
+        - amlogic,meson8b-uart
+        - amlogic,meson-gx-uart
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: external xtal clock identifier
+      - description: the bus core clock, either the clk81 clock or the gate clock
+      - description: the source of the baudrate generator, can be either the xtal or the pclk
+
+  clock-names:
+    items:
+      - const: xtal
+      - const: pclk
+      - const: baud
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+examples:
+  - |
+    serial@84c0 {
+          compatible = "amlogic,meson-gx-uart";
+          reg = <0x84c0 0x14>;
+          interrupts = <26>;
+          clocks = <&xtal>, <&pclk>, <&xtal>;
+          clock-names = "xtal", "pclk", "baud";
+    };