dt-bindings: arm: Add Versatile YAML schema

This implements the top-level schema for the ARM Versatile
platforms.

Cc: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/arm/arm,versatile.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/arm,versatile.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM Versatile Boards Device Tree Bindings
+
+maintainers:
+  - Linus Walleij <linus.walleij@linaro.org>
+
+description: |+
+  The ARM Versatile boards are two variants of ARM926EJ-S evaluation boards
+  with various pluggable interface boards, in essence the Versatile PB version
+  is a superset of the Versatile AB version.
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    oneOf:
+      - description: The ARM Versatile Application Baseboard (HBI-0118) is an
+          evaluation board specifically for the ARM926EJ-S. It can be connected
+          to an IB1 interface board for a touchscreen-type use case or an IB2
+          for a candybar phone-type use case. See ARM DUI 0225D.
+        items:
+          - const: arm,versatile-ab
+      - description: The ARM Versatile Platform Baseboard (HBI-0117) is an
+          extension of the Versatile Application Baseboard that includes a
+          PCI host controller. Like the sibling board, it is done specifically
+          for ARM926EJ-S. See ARM DUI 0224B.
+        items:
+          - const: arm,versatile-pb
+
+  core-module@10000000:
+    type: object
+    description: the root node in the Versatile platforms must contain
+      a core module child node. They are always at physical address
+      0x10000000 in all the Versatile variants.
+    properties:
+      compatible:
+        items:
+          - const: arm,core-module-versatile
+          - const: syscon
+          - const: simple-mfd
+      reg:
+        maxItems: 1
+
+    required:
+      - compatible
+      - reg
+
+patternProperties:
+  "^syscon@[0-9a-f]+$":
+    type: object
+    description: When fitted with the IB2 Interface Board, the Versatile
+      AB will present an optional system controller node which controls the
+      extra peripherals on the interface board.
+    properties:
+      compatible:
+        contains:
+          const: arm,versatile-ib2-syscon
+    required:
+      - compatible
+      - reg
+
+required:
+  - compatible
+  - core-module@10000000
+
+...