CONFIG_ARCH_IXDP425 is not available for the default architecture x86.
Result is shown for architecture arm


configname: CONFIG_ARCH_IXDP425

Linux Kernel Configuration
└─> Intel IXP4xx Implementation Options
└─> IXDP425

Say 'Y' here if you want your kernel to support Intel's
IXDP425 Development Platform (Also known as Richfield).
For more information on this platform, see <file:Documentation/arm/IXP4xx>.