drm/panel: Add support for the Raspberry Pi 7" Touchscreen.

This driver communicates with the Atmel microcontroller for sequencing
the poweron of the TC358762 DSI-DPI bridge and controlling the
backlight PWM.

v2: Set the same default orientation as the closed source firmware
    used, which is the best for viewing angle.
v3: Rewrite as an i2c client driver after bridge driver rejection.
v4: Finish probe without the DSI host, using the new delayed
    registration, and attach to the host during mipi_dsi_driver probe.
v5: Rework to drop the "probe without DSI host" mode again, now that
    vc4 will create the host early on.
v6: Drop unused brightness #define (noticed by Thierry)

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20170927193654.12609-4-eric@anholt.net
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Acked-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/panel/Kconfig

@@ -82,6 +82,14 @@ config DRM_PANEL_PANASONIC_VVX10F034N00
 	  WUXGA (1920x1200) Novatek NT1397-based DSI panel as found in some
 	  Xperia Z2 tablets
 
+config DRM_PANEL_RASPBERRYPI_TOUCHSCREEN
+	tristate "Raspberry Pi 7-inch touchscreen panel"
+	depends on DRM_MIPI_DSI
+	help
+	  Say Y here if you want to enable support for the Raspberry
+	  Pi 7" Touchscreen.  To compile this driver as a module,
+	  choose M here.
+
 config DRM_PANEL_SAMSUNG_S6E3HA2
 	tristate "Samsung S6E3HA2 DSI video mode panel"
 	depends on OF

drivers/gpu/drm/panel/Makefile

@@ -5,6 +5,7 @@ obj-$(CONFIG_DRM_PANEL_JDI_LT070ME05000) += panel-jdi-lt070me05000.o
 obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o
 obj-$(CONFIG_DRM_PANEL_ORISETECH_OTM8009A) += panel-orisetech-otm8009a.o
 obj-$(CONFIG_DRM_PANEL_PANASONIC_VVX10F034N00) += panel-panasonic-vvx10f034n00.o
+obj-$(CONFIG_DRM_PANEL_RASPBERRYPI_TOUCHSCREEN) += panel-raspberrypi-touchscreen.o
 obj-$(CONFIG_DRM_PANEL_SAMSUNG_LD9040) += panel-samsung-ld9040.o
 obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6E3HA2) += panel-samsung-s6e3ha2.o
 obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6E63J0X03) += panel-samsung-s6e63j0x03.o