drm/bridge: Add Analogix anx78xx support

Although there are other chips from the same family that can reuse this
driver, at the moment we only tested ANX7814 chip.

The ANX7814 is an ultra-low power Full-HD (1080p60) SlimPort transmitter
designed for portable devices. This driver adds initial support for HDMI
to DP pass-through mode.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Daniel Kurtz <djkurtz@chromium.org>
Cc: Nicolas Boichat <drinkcat@chromium.org>
Cc: Thierry Reding <treding@nvidia.com>
[treding@nvidia.com: coding style, propagate regulator_get() errors]
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/bridge/Kconfig

@@ -7,6 +7,16 @@ config DRM_BRIDGE
 menu "Display Interface Bridges"
 	depends on DRM && DRM_BRIDGE
 
+config DRM_ANALOGIX_ANX78XX
+	tristate "Analogix ANX78XX bridge"
+	select DRM_KMS_HELPER
+	select REGMAP_I2C
+	---help---
+	  ANX78XX is an ultra-low Full-HD SlimPort transmitter
+	  designed for portable devices. The ANX78XX transforms
+	  the HDMI output of an application processor to MyDP
+	  or DisplayPort.
+
 config DRM_DW_HDMI
 	tristate
 	select DRM_KMS_HELPER

drivers/gpu/drm/bridge/Makefile

@@ -1,5 +1,6 @@
 ccflags-y := -Iinclude/drm
 
+obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
 obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
 obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o