To begin, an Info manual is either nonsplit (contained wholly within a single file) or split (across several files).
The syntax for a nonsplit manual is:
<nonsplit info file> = <preamble> <node>* <tag table> (<local variables>)?
When split, there is a main file, which contains only pointers to the nodes given in other subfiles. The main file looks like this:
<split info main file> = <preamble> <indirect table> <tag table> (<local variables>)?
The subfiles in a split manual have the following syntax:
<split info subfile> = <preamble> <node>*