AT91 USART Driver

modulename: at91-usart.ko

configname: CONFIG_MFD_AT91_USART

Linux Kernel Configuration
└─>Device Drivers
└─>Multifunction device drivers
└─>AT91 USART Driver
In linux kernel since version 3.10 (release Date: 2013-06-30)  
Select this to get support for AT91 USART IP. This is a wrapper
over at91-usart-serial driver and usart-spi-driver. Only one function
can be used at a time. The choice is done at boot time by the probe
function of this MFD driver according to a device tree property.

source code:
selects
CONFIG_MFD_CORE


is depended by
CONFIG_SERIAL_ATMEL