[PATCH v9 1/2] dt-bindings: usb: cdns3: Add cdns,cdnsp compatible string

[Pawel Laszczak via B4 Relay]

From: Pawel Laszczak <pawell@xxxxxxxxxxx>

Introduce a new generic fallback compatible string 'cdns,cdnsp' for
Cadence USBSSP controllers to support hardware configurations where
the Dual-Role Device (DRD) register block is missing or inaccessible.

Following the maintainer's feedback, avoid generic property-like naming
(such as "-no-drd") and use a clean generic fallback. To keep the schema
resource-driven and strictly validated, define a two-string compatible
matrix using an empty schema ({}) wildcard. This allows future vendor
SoC compatibles to be prepended while safely falling back to the 2-resource
USBSSP configuration.

When 'cdns,cdnsp' is matched:
- The 'otg' register and interrupt resources are not required.
- The 'reg' and 'interrupts' properties are restricted to 2 items
  (host and device).
- 'dr_mode' must be explicitly set to either 'host' or 'peripheral'.

The standard 'cdns,usb3' compatible remains unchanged, maintaining
backward compatibility by requiring all 3 resource sets (otg, host, dev).

Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
---
v9:
- Dropped the "cdns,cdnsp-no-drd" string to avoid generic property-like
  naming as requested by Conor.
- Introduced the clean generic fallback "cdns,cdnsp".

v8:
- Update commit message to reflect schema changes.
- Removed 'cdns,no-drd' boolean property as per Rob Herring's suggestion.
- Introduced a new compatible string 'cdns,cdnsp-no-drd' for controller
  variants that lack the DRD/OTG register block.

v7:
- Rename 'no_drd' to 'cdns,no-drd'.
- Update commit message to reflect property renaming and schema changes.
- Simplify 'reg-names' using a single enum.
- Revert 'interrupt-names' to a list of constants.
- Move 'reg' item descriptions to if/else blocks for accuracy.
- Clean up 'if/then' logic (remove redundant checks).
- Add explicit 'items' list for 'interrupt-names' in the 'else' block.

v6:
- Fixed validation error for 'interrupt-names' by correcting
  the items definition.
- Adjusted 'minItems'/'maxItems' to properly support the optional
 'wakeup' interrupt.
- Fixed 'too long' schema error in examples.

v5:
- Implemented strict conditional validation using if-then-else logic.
- Enforced 2 register/interrupt items and required 'dr_mode'
  (host or peripheral) when 'no_drd' is present.
- Enforced the standard 3 register/interrupt items (otg, host, dev)
  when 'no_drd' is absent to ensure backward compatibility.
- Updated 'reg-names' and 'interrupt-names' to use enums in the main
  properties section to support flexible resource ordering during
  validation.
---
---
 .../devicetree/bindings/usb/cdns,usb3.yaml         | 63 ++++++++++++++++++----
 1 file changed, 53 insertions(+), 10 deletions(-)

diff --git a/Documentation/devicetree/bindings/usb/cdns,usb3.yaml b/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
index 2d95fb7321af..e8082c5c05a2 100644
--- a/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
+++ b/Documentation/devicetree/bindings/usb/cdns,usb3.yaml
@@ -17,22 +17,24 @@ description:
 
 properties:
   compatible:
-    const: cdns,usb3
+    oneOf:
+      - const: cdns,usb3
+      - items:
+          - {}
+          - const: cdns,cdnsp
 
   reg:
-    items:
-      - description: OTG controller registers
-      - description: XHCI Host controller registers
-      - description: DEVICE controller registers
+    minItems: 2
+    maxItems: 3
 
   reg-names:
+    minItems: 2
+    maxItems: 3
     items:
-      - const: otg
-      - const: xhci
-      - const: dev
+      enum: [ otg, xhci, dev ]
 
   interrupts:
-    minItems: 3
+    minItems: 2
     items:
       - description: XHCI host controller interrupt
       - description: Device controller interrupt
@@ -41,7 +43,7 @@ properties:
                      cleared by xhci core, this interrupt is optional
 
   interrupt-names:
-    minItems: 3
+    minItems: 2
     items:
       - const: host
       - const: peripheral
@@ -93,6 +95,47 @@ allOf:
   - $ref: usb-drd.yaml#
   - $ref: usb-xhci.yaml#
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: cdns,cdnsp
+    then:
+      properties:
+        reg:
+          items:
+            - description: XHCI Host controller registers
+            - description: DEVICE controller registers
+        reg-names:
+          items:
+            - const: xhci
+            - const: dev
+        interrupts:
+          maxItems: 2
+        interrupt-names:
+          items:
+            - const: host
+            - const: peripheral
+        dr_mode:
+          enum: [host, peripheral]
+    else:
+      properties:
+        reg:
+          items:
+            - description: OTG controller registers
+            - description: XHCI Host controller registers
+            - description: DEVICE controller registers
+        reg-names:
+          items:
+            - const: otg
+            - const: xhci
+            - const: dev
+        interrupts:
+          minItems: 3
+          maxItems: 4
+        interrupt-names:
+          minItems: 3
+
 unevaluatedProperties: false
 
 examples:

-- 
2.43.0