dt-bindings: arm: socionext: add Synquacer platforms

Socionext's DeveloperBox is based on the SC2A11B SoC (Synquacer).
Specify bindings for the platform and boards based on that.
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Link: https://lore.kernel.org/r/20230621153658.60646-1-jaswinder.singh@linaro.orgSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/socionext/synquacer.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/socionext/synquacer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Socionext Synquacer platform
+
+maintainers:
+  - Masahisa Kojima <masahisa.kojima@linaro.org>
+  - Jassi Brar <jaswinder.singh@linaro.org>
+
+description:
+  Socionext SC2A11B (Synquacer) SoC based boards
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - socionext,developer-box
+          - const: socionext,synquacer
+
+additionalProperties: true
+
+...