dt-bindings: display: Add Synopsys DW MIPI DSI host controller

This patch adds documentation of device tree bindings for the
Synopsys DesignWare MIPI DSI host controller.
Signed-off-by: Philippe CORNU <philippe.cornu@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1500277223-29553-4-git-send-email-philippe.cornu@st.com

Documentation/devicetree/bindings/display/bridge/dw_mipi_dsi.txt

+Synopsys DesignWare MIPI DSI host controller
+============================================
+
+This document defines device tree properties for the Synopsys DesignWare MIPI
+DSI host controller. It doesn't constitue a device tree binding specification
+by itself but is meant to be referenced by platform-specific device tree
+bindings.
+
+When referenced from platform device tree bindings the properties defined in
+this document are defined as follows. The platform device tree bindings are
+responsible for defining whether each optional property is used or not.
+
+- reg: Memory mapped base address and length of the DesignWare MIPI DSI
+  host controller registers. (mandatory)
+
+- clocks: References to all the clocks specified in the clock-names property
+  as specified in [1]. (mandatory)
+
+- clock-names:
+  - "pclk" is the peripheral clock for either AHB and APB. (mandatory)
+  - "px_clk" is the pixel clock for the DPI/RGB input. (optional)
+
+- resets: References to all the resets specified in the reset-names property
+  as specified in [2]. (optional)
+
+- reset-names: string reset name, must be "apb" if used. (optional)
+
+- panel or bridge node: see [3]. (mandatory)
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+[2] Documentation/devicetree/bindings/reset/reset.txt
+[3] Documentation/devicetree/bindings/display/mipi-dsi-bus.txt