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 <http://www.linux-xtensa.org/>.

source code:

drivers/irqchip/irq-xtensa-pic.c