say how the docs are handled and generated

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@36436 15284696-431f-4ddb-bdfa-cd5b030d7da7

SUBMITTING_DOCS

@@ -13,6 +13,24 @@ care of following rules:
 [ see SUBMITTING_PYTHON for Python code hints ]
 
 
+0. Introduction
+
+   There are two types of documentation
+   - Libraries programmers docs: we use doxygen and document the functions 
+      directly in the source code. See lib/*/*.c and lib/*/*.dox for examples
+
+   - User manual: we write it in simple HTML, storing the manual in a 
+      file '<module>.html' within the subdirectory of the module.
+      The file contains no header nor footer. The complete HTML file is
+      autogenerated during the compilation process (indeed, it is generated
+      in a virtual session directly after compilation of the module).
+      In this virtual session the module is called internally with
+      --html-description which generates the parameters/flags list in
+      HTML format, along with '<module>.html', HTML header and footer
+      the final HTML manual page is created and stored in the target
+      binaries directory. In a separate process the MAN format is 
+      generated from the complete HTML files.
+
 1. Editing of HTML pages
    To avoid insertion of too complicated HTML tags (see also below),
    we strongly suggest to use a plain text editor rather than a