dt-bindings: arm: add bcmbca device tree binding document

Add arch bcmbca device tree binding document for Broadcom ARM based
broadband SoC chipsets. In this change, only BCM47622 is added. Other
chipsets will be added in the future.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

Documentation/devicetree/bindings/arm/bcm/brcm,bcmbca.yaml

@@ -0,0 +1,33 @@
+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/bcm/brcm,bcmbca.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom Broadband SoC device tree bindings
+
+description:
+  Broadcom Broadband SoCs include family of high performance DSL/PON/Wireless
+  chips that can be used as home gateway, router and WLAN AP for residential,
+  enterprise and carrier applications.
+
+maintainers:
+  - William Zhang <william.zhang@broadcom.com>
+  - Anand Gore <anand.gore@broadcom.com>
+  - Kursad Oney <kursad.oney@broadcom.com>
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    oneOf:
+      - description: BCM47622 based boards
+        items:
+          - enum:
+              - brcm,bcm947622
+          - const: brcm,bcm47622
+          - const: brcm,bcmbca
+
+additionalProperties: true
+
+...