Update of "Introduction" section

Workflow for documentation production in OSM.md

@@ -2,17 +2,16 @@
 
 ## Introduction
 
-About roles:
-
-- Contributors
-- Editor/Reviewer
-  - Duties
-  - Permissions
-
 The process is based on:
 
 - Text-based edition with Markdown
-- Version control with Git, using ETSI's Gitlab respos
+- Further conversion to multiple formats and templates with Pandoc
+- Version control with Git, using ETSI's Gitlab
+
+In the edition process there are two roles:
+
+- **Contributors.** Anyone contributing content to a given document, with no special privileges. They cannot contribute directly to `master` branch, so they have to contribute pushing branches and issuing a _merge request_ (i.e. requesting their intergration).
+- **Editor/Reviewer**. The person (or people) in charge of integrating (_merging_) contributions into the main document. In consequence, they can push changes directly to the `master` branch. They should also decide the document split in different files and provide the means to build and convert the document to a given set of target formats and templates.
 
 ## Software requirements