Info-find-node-in-buffer is a compiled Lisp function in `info.el'.

(Info-find-node-in-buffer REGEXP &optional STRICT-CASE)

Find a node or anchor in the current buffer.
REGEXP is a regular expression matching nodes or references. Its first
group should match `Node:' or `Ref:'.
Value is the position at which a match was found, or nil if not found.
This function looks for a case-sensitive match first. If none is found,
a case-insensitive match is tried (unless optional argument STRICT-CASE
is non-nil).