Where is logback encoder pattern documentation

I've gone through all the documentation of logback and I can't find anywhere the documentation to configure the encoder's pattern when logging, such as:

<encoder>
  <pattern>%d{HH:mm:ss.SSS} %-4relative %-5level %logger{35} - %msg%n</pattern>
</encoder>

I would like a table (like the one that log4j has) explaining the different options to configure the pattern.

Where is the documentation of the pattern? Maybe they are defined in another project?