dt-bindings: arm: amlogic: amlogic,meson-gx-ao-secure: convert to yaml

Now that we have the DT validation in place, let's convert the device tree
bindings for the Amlogic Always-On Secure Registers over to a YAML schemas.
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/amlogic/amlogic,meson-gx-ao-secure.txt

-Amlogic Meson Firmware registers Interface
-------------------------------------------
-
-The Meson SoCs have a register bank with status and data shared with the
-secure firmware.
-
-Required properties:
- - compatible: For Meson GX SoCs, must be "amlogic,meson-gx-ao-secure", "syscon"
-
-Properties should indentify components of this register interface :
-
-Meson GX SoC Information
-------------------------
-A firmware register encodes the SoC type, package and revision information on
-the Meson GX SoCs.
-If present, the following property should be added :
-
-Optional properties:
-  - amlogic,has-chip-id: If present, the interface gives the current SoC version.
-
-Example
--------
-
-ao-secure@140 {
-	compatible = "amlogic,meson-gx-ao-secure", "syscon";
-	reg = <0x0 0x140 0x0 0x140>;
-	amlogic,has-chip-id;
-};

Documentation/devicetree/bindings/arm/amlogic/amlogic,meson-gx-ao-secure.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2019 BayLibre, SAS
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/arm/amlogic/amlogic,meson-gx-ao-secure.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Amlogic Meson Firmware registers Interface
+
+maintainers:
+  - Neil Armstrong <narmstrong@baylibre.com>
+
+description: |
+  The Meson SoCs have a register bank with status and data shared with the
+  secure firmware.
+
+# We need a select here so we don't match all nodes with 'syscon'
+select:
+  properties:
+    compatible:
+      contains:
+        const: amlogic,meson-gx-ao-secure
+  required:
+    - compatible
+
+properties:
+  compatible:
+   items:
+      - const: amlogic,meson-gx-ao-secure
+      - const: syscon
+
+  reg:
+    maxItems: 1
+
+  amlogic,has-chip-id:
+    description: |
+      A firmware register encodes the SoC type, package and revision
+      information on the Meson GX SoCs. If present, the interface gives
+      the current SoC version.
+    type: boolean
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    ao-secure@140 {
+          compatible = "amlogic,meson-gx-ao-secure", "syscon";
+          reg = <0x140 0x140>;
+          amlogic,has-chip-id;
+    };