A description of the options accepted by spatch is available here.

A grammar of the SmPL language is available in pdf or html. This document also contains some annotated examples.

More examples are available here.

The LWN articles about Coccinelle may provide a useful introduction: Semantic patching with Coccinelle by Valerie Aurora, and Evolutionary development of a semantic patch using Coccinelle by Wolfram Sang. Eric Leblond has also written an article about his experiences.

An introductory lecture is available here.