man: Clarify that deb-symbols(5) documents the binary format subset

The template symbol files are described in dpkg-gensymbols(1).

Closes: #795163

debian/changelog

@@ -67,6 +67,9 @@ dpkg (1.18.5) UNRELEASED; urgency=medium
     - Clarify that packages are only automatically forgotten by dpkg if they
       contain no user data, such as package selections. Closes: #813179
     - Fix documentation for package flags in dpkg(1).
+    - Clarify that deb-symbols(5) documents the binary format subset, and
+      the template symbol files are described in dpkg-gensymbols(1).
+      Closes: #795163
 
   [ Updated programs translations ]
   * Portuguese (Miguel Figueiredo).

man/deb-symbols.5

@@ -24,6 +24,10 @@ deb\-symbols \- Debian's extended shared library information file
 symbols
 .
 .SH DESCRIPTION
+The symbol files are shipped in Debian binary packages, and its format
+is a subset of the template symbol files used by \fBdpkg\-gensymbols\fP(1)
+in Debian source packages.
+.P
 The format for an extended shared library dependency information entry
 in these files is:
 .PP