[PATCH v4] dt-bindings: display: renesas: du: Document optional reset properties

[Geert Uytterhoeven <geert+renesas@glider.be>]

Document the optional properties for describing module resets, to
support resetting display channels on R-Car Gen2 and Gen3.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
---
v4:
  - Use "All but R8A7779" instead of "R8A779[0123456]", to reduce future
    churn,

v3:
  - Add Acked-by,
  - Drop LVDS resets, as LVDS is now covered by a separate binding,
  - Update the example.

v2:
  - s/phandles/phandle/.
---
 .../devicetree/bindings/display/renesas,du.txt         | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/renesas,du.txt b/Documentation/devicetree/bindings/display/renesas,du.txt
index c97dfacad28118fa..59be7462a4c8bb8e 100644
--- a/Documentation/devicetree/bindings/display/renesas,du.txt
+++ b/Documentation/devicetree/bindings/display/renesas,du.txt
@@ -45,6 +45,14 @@ Required Properties:
     instance that serves the DU channel, and the channel index identifies the
     LIF instance in that VSP.
 
+Optional properties:
+  - resets: A list of phandle + reset-specifier pairs, one for each entry in
+    the reset-names property.
+  - reset-names: Names of the resets. This property is model-dependent.
+    - All but R8A7779 use one reset for a group of one or more successive
+      channels. The resets must be named "du.x" with "x" being the numerical
+      index of the lowest channel in the group.
+
 Required nodes:
 
 The connections to the DU output video ports are modeled using the OF graph
@@ -90,6 +98,8 @@ Example: R8A7795 (R-Car H3) ES2.0 DU
 			 <&cpg CPG_MOD 722>,
 			 <&cpg CPG_MOD 721>;
 		clock-names = "du.0", "du.1", "du.2", "du.3";
+		resets = <&cpg 724>, <&cpg 722>;
+		reset-names = "du.0", "du.2";
 		vsps = <&vspd0 0>, <&vspd1 0>, <&vspd2 0>, <&vspd0 1>;
 
 		ports {
-- 
2.17.1