It looks like Apache project took efforts to provide bridge from Log4j v2 to Slf4j.

Main entry point for Slf4j bridge documentation is on page: https://www.slf4j.org/legacy.html

Also pictures ant text miss Log4j2 on pages: https://www.slf4j.org/manual.html and https://www.slf4j.org/faq.html

External documentation is available on:

https://logging.apache.org/log4j/2.0/log4j-slf4j-impl/ (The Log4j 2 to SLF4J adapter is dependent on the Log4j 2 API and the SLF4J API)

https://logging.apache.org/log4j/2.0/faq.html (You can use the log4j-to-slf4j adapter jar when your application calls the Log4j 2 API and you want to route logging calls to a SLF4J implementation)