How to allow each company section to manage their own content on the Intranet? I have a simple problem of permissions. I work in a company which is divided into different sections. I have to make a Drupal intranet for them.

Each section must be able to manage their own content on the Intranet. The contents of the intranet are always the same, ie the same "content type" with the same "fields". It is necessary that a section could only edit the contents within its section. Thus, "computer" could only create / edit / delete content of "computer". The section of "press" could only create / edit / delete content of "press". All sections can view all content.

I tried different modules. "Field permissions", which lets you field level permissions, is interesting but does not help in this case. "Content Access" allows me to level management content type, but I can do what necesito.Con "Taxanomy Access Control" can define visibility rules, editing and deletion according to the presence or absence of one or more terms a taxonomy. It could be interesting, was not that "computer" should not be able to create content "press", for example.

You could create a content type for each section equal, and each give the required roles. The problem is that they are over 15 and does not seem the most optimal way to do this, because if I have to add a field so I have to do in the 15 (DRY).

I sense that Drupal has a more efficient way of doing this, but as I am new to this CMS I can not find it.
The thing you are looking for is Organic groups. It does exactly what you need.
Further more you may be interested in some solutions already made on drupal. Like Open Atrium or Drupal Commons

Hope it helps.