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

CONFIG_XTENSA (not configurable)

modulename: irq-xtensa-pic.ko

configname: CONFIG_XTENSA

Linux Kernel Configuration
In linux kernel since version 2.6.13 (release Date: 2005-08-28)  
Xtensa processors are 32-bit RISC machines designed by Tensilica
primarily for embedded systems. These processors are both
configurable and extensible. The Linux port to the Xtensa
architecture supports all processor configurations and extensions,
with reasonable minimum requirements. The Xtensa Linux project has
a home page at <>.

source code: