Hello ! First, sorry for my poor English (I'm French)...
I want to create modules in module but I don't know if it's possible since I don't find any documentation or questions about this on internet and in the documentation. To make it clear I want to have a structure like this :
A module is a self-contained group of classes, views, config, language files, etc., so its functionality can be re-used in different applications.
There is no direct relation to the segments in the URL, other than that the first segment must be the module name (to speedup controller lookup.
If you really want seperate modules (in the definition above), you can only do that through routing, by routing 'parentmodule/submodule1/:any' to 'submodule1/$1, and route "submodule1/:any" to your 404 handler.
If you just want different levels of controllers within the same module, just create the controller:
modules/parentmodule/classes/controller/submodule1/myclass.php, and define it as
Namespace Parentmodule;
class Controller_Submodule1_Myclass extends \Controller