dt-bindings: arm: bcm: add BCM53573 SoCs family binding

BCM53573 is a family derived from Northstar with some important
differences:
1. Cortex-A9 replaced by Cortex-A7
2. XHCI controller dropped
3. Two Ethernet interfaces removed
4. Two 802.11ac cores embedded

Linux already contains DTS files for some on those devices so add a
proper binding for it.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230710175944.32631-1-zajec5@gmail.com
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>

Documentation/devicetree/bindings/arm/bcm/brcm,bcm53573.yaml

@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/bcm/brcm,bcm53573.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Broadcom BCM53573 SoCs family
+
+description:
+  Broadcom BCM53573 / BCM47189 Wi-Fi SoCs derived from Northstar.
+
+maintainers:
+  - Rafał Miłecki <rafal@milecki.pl>
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    oneOf:
+      - description: BCM53573 based boards
+        items:
+          - enum:
+              - tenda,ac6-v1
+              - tenda,w15e-v1
+          - const: brcm,bcm53573
+
+      - description: BCM47189 based boards
+        items:
+          - enum:
+              - brcm,bcm947189acdbmr
+              - luxul,xap-810-v1
+              - luxul,xap-1440-v1
+              - tenda,ac9
+          - const: brcm,bcm47189
+          - const: brcm,bcm53573
+
+additionalProperties: true
+
+...