CONFIG_ARCH_PNX4008 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Philips Nexperia PNX4008 Mobile

configname: CONFIG_ARCH_PNX4008

ARM system type
└─>Philips Nexperia PNX4008 Mobile
In linux kernel since version 2.6.18 (release Date: 2006-09-19)  
This enables support for Philips PNX4008 mobile platform.

is selected by
CONFIG_CPU_ARM926T