dt-bindings: drm/msm/gpu: document second interconnect

Some A3xx and all A4xx Adreno GPUs do not have GMEM inside the GPU core
and must use the On Chip MEMory (OCMEM) in order to be functional.
There's a separate interconnect path that needs to be setup to OCMEM.
Let's document this second interconnect path that's available. Since
there's now two available interconnects, let's add the
interconnect-names property.

Signed-off-by: Brian Masney <masneyb@onstation.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

Documentation/devicetree/bindings/display/msm/gpu.txt

@@ -23,7 +23,10 @@ Required properties:
 - iommus: optional phandle to an adreno iommu instance
 - operating-points-v2: optional phandle to the OPP operating points
 - interconnects: optional phandle to an interconnect provider.  See
-  ../interconnect/interconnect.txt for details.
+  ../interconnect/interconnect.txt for details. Some A3xx and all A4xx platforms
+  will have two paths; all others will have one path.
+- interconnect-names: The names of the interconnect paths that correspond to the
+  interconnects property. Values must be gfx-mem and ocmem.
 - qcom,gmu: For GMU attached devices a phandle to the GMU device that will
   control the power for the GPU. Applicable targets:
     - qcom,adreno-630.2
@@ -76,6 +79,7 @@ Example a6xx (with GMU):
 		operating-points-v2 = <&gpu_opp_table>;
 
 		interconnects = <&rsc_hlos MASTER_GFX3D &rsc_hlos SLAVE_EBI1>;
+		interconnect-names = "gfx-mem";
 
 		qcom,gmu = <&gmu>;