CONFIG_ACPI_PROCESSOR_IDLE (not configurable)

configname: CONFIG_ACPI_PROCESSOR_IDLE

Linux Kernel Configuration
└─>Power management and ACPI options
└─>ACPI (Advanced Configuration and Power Interface) Support
└─>ACPI_PROCESSOR_IDLE
In linux kernel since version 3.10 (release Date: 2013-06-30)  
selects
CONFIG_CPU_IDLE

depends
CONFIG_ACPI

is depended by
CONFIG_ACPI_PROCESSOR