CONFIG_SERIAL_MCTRL_GPIO (not configurable)

modulename: serial_mctrl_gpio.ko

configname: CONFIG_SERIAL_MCTRL_GPIO

Linux Kernel Configuration
└─>Device Drivers
└─>Character devices
└─>SERIAL_MCTRL_GPIO
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
drivers/tty/serial/serial_mctrl_gpio.c
depends
CONFIG_TTY