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

NexVision OTOM Board

modulename: mach-otom.ko

and/or

configname: CONFIG_MACH_OTOM

Linux Kernel Configuration
└─>Samsung S3C24XX SoCs (deprecated, see help)
└─>Samsung S3C24XX SoCs Support
└─>NexVision OTOM Board
In linux kernel since version 2.6.12  
Say Y here if you are using the Nex Vision OTOM board