drm/panel: Add Rocktech jh057n00900 panel driver

Support Rocktech jh057n00900 5.5" 720x1440 TFT LCD panel. It is a MIPI
DSI video mode panel.

The panel seems to use a Sitronix ST7703 look alike (most of the
commands look similar to the ST7703's data sheet but use a different
number of parameters). The initial version of the DSI init sequence
(including sleeps) were provided by the vendor. Sleeps were reduced
considerably though to speed up initialization.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1a9ce687be283c66dfb26d1dfb52a7bf695090fa.1554114302.git.agx@sigxcpu.org

drivers/gpu/drm/panel/Kconfig

@@ -158,6 +158,19 @@ config DRM_PANEL_RAYDIUM_RM68200
 	  Say Y here if you want to enable support for Raydium RM68200
 	  720x1280 DSI video mode panel.
 
+config DRM_PANEL_ROCKTECH_JH057N00900
+	tristate "Rocktech JH057N00900 MIPI touchscreen panel"
+	depends on OF
+	depends on DRM_MIPI_DSI
+	depends on BACKLIGHT_CLASS_DEVICE
+	help
+	  Say Y here if you want to enable support for Rocktech JH057N00900
+	  MIPI DSI panel as e.g. used in the Librem 5 devkit. It has a
+	  resolution of 720x1440 pixels, a built in backlight and touch
+	  controller.
+	  Touch input support is provided by the goodix driver and needs to be
+	  selected separately.
+
 config DRM_PANEL_RONBO_RB070D30
 	tristate "Ronbo Electronics RB070D30 panel"
 	depends on OF