[PATCH v2 3/9] dt-bindings: media: snps,dw-hdmi-rx: add a port for a bridge in front

[Sascha Hauer]

Describe the OF graph port connecting the receiver to an HDMI bridge in
front of it. The schema sets additionalProperties: false, so without
this a device tree carrying the endpoint does not validate at all.

hpd-gpios is the +5V line of the HDMI connector, which the source drives
to announce itself. On a board whose HDMI connector belongs to such a
bridge, that line goes to the bridge and there is nothing for the
receiver to sense, so the property cannot be provided. The name is
unfortunate: the hot plug detect line the receiver drives back at the
source is a controller register, not this GPIO. Describe what it
actually carries.

A board has either the connector wired to the receiver or a bridge in
front of it, so require exactly one of hpd-gpios and port.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
 .../devicetree/bindings/media/snps,dw-hdmi-rx.yaml  | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/media/snps,dw-hdmi-rx.yaml b/Documentation/devicetree/bindings/media/snps,dw-hdmi-rx.yaml
index b7f6c87d0e06a..896f8ffbb5bf9 100644
--- a/Documentation/devicetree/bindings/media/snps,dw-hdmi-rx.yaml
+++ b/Documentation/devicetree/bindings/media/snps,dw-hdmi-rx.yaml
@@ -63,9 +63,21 @@ properties:
     maxItems: 1
 
   hpd-gpios:
-    description: GPIO specifier for HPD.
+    description:
+      The +5V line of the HDMI connector, which the source drives to announce
+      itself. Despite the name this is an input to the receiver; the hot plug
+      detect line the receiver drives back at the source is handled inside the
+      controller. Absent when the connector belongs to a bridge in front of
+      this receiver rather than to the receiver itself.
     maxItems: 1
 
+  port:
+    $ref: /schemas/graph.yaml#/properties/port
+    description:
+      Connection to the HDMI source. Present when an HDMI bridge sits in
+      front of this receiver instead of the connector being wired straight
+      to it.
+
   rockchip,grf:
     $ref: /schemas/types.yaml#/definitions/phandle
     description:
@@ -88,7 +100,12 @@ required:
   - power-domains
   - resets
   - pinctrl-0
-  - hpd-gpios
+
+oneOf:
+  - required:
+      - hpd-gpios
+  - required:
+      - port
 
 additionalProperties: false
 

-- 
2.47.3