Building with the attached random configuration file,
drivers/built-in.o: In function `sc16is7xx_i2c_probe':
/home/jim/linux/drivers/tty/serial/sc16is7xx.c:1347: undefined
reference to `devm_regmap_init_i2c'
drivers/built-in.o: In function `sc16is7xx_init':
/home/jim/linux/drivers/tty/serial/sc16is7xx.c:1387: undefined
reference to `i2c_register_driver'
drivers/built-in.o: In function `sc16is7xx_exit':
/home/jim/linux/drivers/tty/serial/sc16is7xx.c:1408: undefined
reference to `i2c_del_driver'