The phrase "manufacturer customizations" means changes or modifications made by the company that produces a product to meet specific requirements or preferences. Full definition
Google recently released Android 3.1 (the Galaxy Tab 10.1 ships with it) to most existing Honeycomb tablets, and there have thus far been few manufacturer customizations. (pcmag.com)
Almost since Android was introduced, it's been followed by people (including me) complaining about manufacturer customizations to the software. (theverge.com)
Look, there's nothing inherently wrong with the those heavy manufacturer customizations layered on top of Android. (greenbot.com)