CONFIG_SA1100_LART is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

LART

modulename: lart.ko

configname: CONFIG_SA1100_LART

Linux Kernel Configuration
└─>SA11x0 Implementations
└─>LART
In linux kernel since version 2.6.12  
Say Y here if you are using the Linux Advanced Radio Terminal
(also known as the LART). See <http://www.lartmaker.nl/> for
information on the LART.

source code: