CONFIG_MACH_SX1 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Siemens SX1

modulename: board-sx1.ko

configname: CONFIG_MACH_SX1

Linux Kernel Configuration
└─>TI OMAP1
└─>TI OMAP1 specific features
└─>Siemens SX1
In linux kernel since version 2.6.24 (release Date: 2008-01-24)  
Support for the Siemens SX1 phone. To boot the kernel,
you'll need a SX1 compatible bootloader; check out
http://forum.oslik.ru and
https://www.handhelds.org/moin/moin.cgi/SiemensSX1
for more information.
Say Y here if you have such a phone, say NO otherwise.

source code: