Input: add zinitix touchscreen driver

Add support for the bt541 touchscreen IC from zinitix, loosely based on
downstream driver. The driver currently supports multitouch (5 touch points).
The bt541 seems to support touch keys, but the support was not added because
that functionality is not being utilized by the touchscreen used for testing.
Based on the similartities between downstream drivers, it seems likely that
other similar touchscreen ICs can be supported with this driver in the future.

Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
Link: https://lore.kernel.org/r/20201001122949.16846-1-michael.srba@seznam.cz
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/Kconfig

@@ -1322,4 +1322,16 @@ config TOUCHSCREEN_IQS5XX
 	  To compile this driver as a module, choose M here: the
 	  module will be called iqs5xx.
 
+config TOUCHSCREEN_ZINITIX
+	tristate "Zinitix touchscreen support"
+	depends on I2C
+	help
+	  Say Y here if you have a touchscreen using Zinitix bt541,
+	  or something similar enough.
+
+	  If unsure, say N.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called zinitix.
+
 endif

drivers/input/touchscreen/Makefile

@@ -111,3 +111,4 @@ obj-$(CONFIG_TOUCHSCREEN_COLIBRI_VF50)	+= colibri-vf50-ts.o
 obj-$(CONFIG_TOUCHSCREEN_ROHM_BU21023)	+= rohm_bu21023.o
 obj-$(CONFIG_TOUCHSCREEN_RASPBERRYPI_FW)	+= raspberrypi-ts.o
 obj-$(CONFIG_TOUCHSCREEN_IQS5XX)	+= iqs5xx.o
+obj-$(CONFIG_TOUCHSCREEN_ZINITIX)	+= zinitix.o