This is a processor plugin for disassemblers which use IDAPython API, to support the Xtensa core found in Espressif ESP8266. It does not support other configurations of the Xtensa architecture, but that is probably (hopefully) easy to implement. Originally developed for IDA (https://github.com/themadinventor/ida-xtensa), this fork is used almost exclusively with ScratchABit open-source disassembler: https://github.com/pfalcon/ScratchABit .
Copy the file to the plugins/cpu/ directory in your ScratchABit install.
Or:
Copy the file to the procs/ directory in your IDA install.
GPLv2