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

Iskratel Electronics XCEP

modulename: xcep.ko

configname: CONFIG_MACH_XCEP

Linux Kernel Configuration
└─>Intel PXA2xx/PXA3xx Implementations
└─>Iskratel Electronics XCEP
In linux kernel since version 2.6.32 (release Date: 2009-12-02)  
PXA255 based Single Board Computer with SMC 91C111 ethernet chip and 64 MB of flash.
Tuned for usage in Libera instruments for particle accelerators.

source code:
arch/arm/mach-pxa/xcep.c