dt-bindings: display/msm: qcom, sdm845-mdss: document the DP device

Document the DP controller added to the sdm845 display subsystem.
Signed-off-by: NDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: NKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/517447/
Link: https://lore.kernel.org/r/20230109045458.316114-1-dmitry.baryshkov@linaro.orgSigned-off-by: NDmitry Baryshkov <dmitry.baryshkov@linaro.org>

Documentation/devicetree/bindings/display/msm/qcom,sdm845-mdss.yaml

@@ -46,6 +46,12 @@ patternProperties:
       compatible:
         const: qcom,sdm845-dpu
 
+  "^displayport-controller@[0-9a-f]+$":
+    type: object
+    properties:
+      compatible:
+        const: qcom,sdm845-dp
+
   "^dsi@[0-9a-f]+$":
     type: object
     properties: