CONFIG_TOUCHSCREEN_ADS7846=y in kernel config
Compile overlay and add: (maybe different per tablet, goodtft/LCD-show)
dtoverlay=ads7846,cs=1,penirq=25,penirq_pull=2,speed=50000,keep_vref_on=0,swapxy=0,pmax=255,xohms=150,xmin=200,xmax=3900,ymin=200,ymax=3900
Add ADS7846_Touchscreen.idc to /system/usr/idc/
ADS7846_Touchscreen.idc: