As I understand, the matching dpi and size qualifiers for the device are based not on actual screen properties (physical dpi and size), but instead on what was predefined by the device manufacturer.
Is there a list of what abstract dpi/sizes are for different devices?
I think there is some misunderstanding. This isn't a free-for-all where manufacturers can pick whatever they want. It is true that they have some flexibility in picking the density, but not a lot -- ultimately the density combined with the physical screen resolution explicitly results in a screen bucket and the way that mapping happens is specified by the platform. Also, the density selected is almost always going to be what you would expect give the actual DPI of the device. A manufacturer may push that with going to a higher density -- this results in a larger UI on the screen and likely a move down to a lower screen size bucket -- but this is extremely rare.
So. A 320x240 screen can only be a small size low density screen. Nothing else.
Devices with 480x320 screens are universally normal size medium density.
Devices with 480x800 (or x852) screens are the vast majority of the time a normal size high density. There are some rare devices with a large 480x800 screen like the Dell Streak -- these are a medium density screen and large bucket. You can tell a device is like this because... well, it has a large screen. :}
The devices shipping with qHD screens can't go up to the xhdpi bucket (try it, you end up with a screen too small to be compatible), so these are still high density and they are also still normal size because they aren't sufficiently large to be in the large bucket. In other words, this is just another phone screen with a little more space for layout.
The 10" tablets you see are 1280x800 or 1280x720. These are mdpi screens, and in the xlarge bucket.
Android 3.2 is supporting 7" screens which are generally 1024x720 mdpi. These end up in the large size bucket.
There are of course many other screens you can imagine, but I don't know off-hand of devices shipping with them and given that we have already covered small, normal, large, and xlarge there is really nothing too interesting about them. For example a 640x480 phone size screen would be hdpi density and small screen bucket.
Take a look at this page : Wikipedia : List of displays by pixel density
AFAIK, most of the time, dpi and ppi are the same, and it next generalized to HDPI/MDPI/LDPI ( see Android screen ranges ). There are just a very little number of exceptions.
Since latest I/O 2015 here is the list that you can use https://www.google.com/design/tool/devices/
I've found this to be helpful as it is specific to Android: http://en.wikipedia.org/wiki/Comparison_of_Android_devices
The size data comes from Wikipedia, and for a better understanding of Pixel Density, check out this great post by Teehan+Lax.
I found this answer on Android Developers.
Here is a list of devices with their respective DIP buckets. It's far from official or complete, but it's the largest source I have found so far:
http://blog.blundell-apps.com/list-of-android-devices-with-pixel-density-buckets/
Thanks to @Blundell for listing it in the comments.
