dt-bindings: usb: Add Aspeed AST2700 DWC3 controller

The Aspeed AST2700 SoC integrates the Synopsys DesignWare USB3 core with
no vendor glue logic: it is functionally compatible with snps,dwc3, uses
the standard DWC3 clocks, and the only SoC-specific part is a USB3 PHY
that is handled by a separate driver.

Add a dedicated binding document rather than adding the compatible and a
conditional to snps,dwc3.yaml. This follows the established per-vendor DWC3
convention (apple,dwc3.yaml, socionext,uniphier-dwc3.yaml, ...) and keeps
the AST2700-specific constraints - notably the mandatory USB3 PHY - out of
the generic schema.

Signed-off-by: Ryan Chen <ryan_chen@aspeedtech.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260710-xhci-v2-1-f292c4f7339a@aspeedtech.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/usb/aspeed,dwc3.yaml

@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/aspeed,dwc3.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Aspeed SuperSpeed DWC3 USB SoC controller
+
+maintainers:
+  - Ryan Chen <ryan_chen@aspeedtech.com>
+
+description:
+  The common content of the node is defined in snps,dwc3.yaml.
+
+select:
+  properties:
+    compatible:
+      contains:
+        const: aspeed,ast2700-xhci
+  required:
+    - compatible
+
+properties:
+  compatible:
+    items:
+      - const: aspeed,ast2700-xhci
+      - const: snps,dwc3
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Controller bus early clock
+      - description: PHY reference clock
+      - description: Controller suspend clock
+
+  clock-names:
+    items:
+      - const: bus_early
+      - const: ref
+      - const: suspend
+
+  resets:
+    maxItems: 1
+
+  phys:
+    maxItems: 1
+
+  phy-names:
+    const: usb3-phy
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+  - resets
+  - phys
+  - phy-names
+
+allOf:
+  - $ref: snps,dwc3.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/aspeed,ast2700-scu.h>
+    #include <dt-bindings/reset/aspeed,ast2700-scu.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    bus {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        usb@12030000 {
+            compatible = "aspeed,ast2700-xhci", "snps,dwc3";
+            reg = <0x0 0x12030000 0x0 0x10000>;
+            interrupts = <GIC_SPI 30 IRQ_TYPE_LEVEL_HIGH>;
+            clocks = <&syscon0 SCU0_CLK_GATE_PORTAUSB2CLK>,
+                     <&syscon0 SCU0_CLK_U2PHY_REFCLK>,
+                     <&syscon0 SCU0_CLK_U2PHY_CLK12M>;
+            clock-names = "bus_early", "ref", "suspend";
+            resets = <&syscon0 SCU0_RESET_PORTA_XHCI>;
+            pinctrl-names = "default";
+            pinctrl-0 = <&pinctrl_usb3axh_default &pinctrl_usb2axh_default>;
+            phys = <&uphy3a>;
+            phy-names = "usb3-phy";
+            dr_mode = "host";
+        };
+    };