CONFIG_MACH_SX1 is not available for the default architecture x86.
Result is shown for architecture arm

Siemens SX1

modulename: board-sx1.ko
configname: CONFIG_MACH_SX1

Linux Kernel Configuration
└─> TI OMAP1 specific features
└─> Siemens SX1

Support for the Siemens SX1 phone. To boot the kernel,
you'll need a SX1 compatible bootloader; check out and
for more information.
Say Y here if you have such a phone, say NO otherwise.

source code: