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

CONFIG_PLAT_ORION_LEGACY (not configurable)

modulename: irq.ko

configname: CONFIG_PLAT_ORION_LEGACY

Linux Kernel Configuration
└─>System Type
└─>PLAT_ORION_LEGACY
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
arch/arm/plat-orion/