CONFIG_ARCH_W90X900 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Nuvoton W90X900 CPU

configname: CONFIG_ARCH_W90X900

ARM system type
└─>Nuvoton W90X900 CPU
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
Support for Nuvoton (Winbond logic dept.) ARM9 processor,You
can login www.mcuos.com or www.nuvoton.com to know more.


is selected by
CONFIG_W90P910_ETH