dt-bindings: bus: add documentation for Aspeed AHBC

Add device tree binding documentation for the Aspeed
Advanced High-Performance Bus (AHB) Controller.
Signed-off-by: Neal Liu <neal_liu@aspeedtech.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/bus/aspeed,ast2600-ahbc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bus/aspeed,ast2600-ahbc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ASPEED Advanced High-Performance Bus Controller (AHBC)
+
+maintainers:
+  - Neal Liu <neal_liu@aspeedtech.com>
+  - Chia-Wei Wang <chiawei_wang@aspeedtech.com>
+
+description: |
+  Advanced High-performance Bus Controller (AHBC) supports plenty of mechanisms
+  including a priority arbiter, an address decoder and a data multiplexer
+  to control the overall operations of Advanced High-performance Bus (AHB).
+
+properties:
+  compatible:
+    enum:
+      - aspeed,ast2600-ahbc
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    ahbc@1e600000 {
+        compatible = "aspeed,ast2600-ahbc";
+        reg = <0x1e600000 0x100>;
+    };