Eclipse – Tutorial for creating own portlet in liferay with eclipse

If you look at the default workflow definition (singleapprover.xml or similar) you'll see that it defines the responsible roles as "Organization Approver", "Site Approver", "Approver" or "Administrator" (from memory).

You can change this - if that's the only thing you'd like to change, it's even simple to do so directly in the xml file. You'll find it within the plugin or in Liferay's sourcecontrol on github. You probably only need to remove the Administrator from the list of responsible roles, then make the people you want to be responsible member of the "Site Approver" role for their relevant sites.

Done

Edit: I don't fully understand your comment below, but the solution I gave assumes that your users are structured in either organizations or sites - in that case, you can have a user being "Site Approver" or "Organization approver" within that organization. All content that is created within the scope of the site or organization will be required to be approved by the approver within that grouping.

In case you upload all the content in the same site, but have different user's assignments, you'll most likely need to go with some scripted assignments (you can script certain parts of the workflow system) but that would go beyond anything I could explain in a few words here. I could point you to the currently available documentation but I doubt this will be enough to illustrate what I'm talking about - sorry