CONFIG_ARCH_IXP23XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
IXP23XX-based
configname: CONFIG_ARCH_IXP23XX
ARM system type
└─>IXP23XX-based
In linux kernel since version 2.6.17 (release Date: 2006-06-17)
Support for Intel's IXP23xx (XScale) family of processors.