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

CONFIG_KIRKWOOD_LEGACY (not configurable)

modulename: irq.ko

configname: CONFIG_KIRKWOOD_LEGACY

Linux Kernel Configuration
└─>Marvell Kirkwood Implementations
└─>KIRKWOOD_LEGACY
In linux kernel since version 3.12 (release Date: 2013-11-03)  
source code:
/arch/arm/mach-kirkwood/

is depended by
CONFIG_MACH_T5325