CONFIG_VARIANT_IRQ_SWITCH is not available for thedefaultarchitecture x86.
Result is shown for architecture xtensa

CONFIG_VARIANT_IRQ_SWITCH (not configurable)

configname: CONFIG_VARIANT_IRQ_SWITCH

Linux/Xtensa Kernel Configuration
└─>VARIANT_IRQ_SWITCH
In linux kernel since version 2.6.30 (release Date: 2009-06-09)