panel-sitronix-st7789v.c:undefined reference to `of_find_backlight_by_node'

[kbuild test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   249f1efd8e3d58f86469fc305b0eda39db18d7ce
commit: 7142afb3a186ed2cd028318205a4852f04283380 drm/panel: Add driver for sitronix ST7789V LCD controller
date:   7 weeks ago
config: x86_64-randconfig-s3-05280946 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout 7142afb3a186ed2cd028318205a4852f04283380
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   drivers/built-in.o: In function `s6e3ha2_remove':
   panel-samsung-s6e3ha2.c:(.text+0x1cc45f): undefined reference to `backlight_device_unregister'
   drivers/built-in.o: In function `s6e3ha2_probe':
   panel-samsung-s6e3ha2.c:(.text+0x1cd24c): undefined reference to `backlight_device_register'
   panel-samsung-s6e3ha2.c:(.text+0x1cd34d): undefined reference to `backlight_device_unregister'
   drivers/built-in.o: In function `st7789v_probe':
>> panel-sitronix-st7789v.c:(.text+0x1cef6c): undefined reference to `of_find_backlight_by_node'

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