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>*
Note that the tag table is not optional for split files, as it is used with the indirect table to deduce which subfile a particular node is in.