Is it possible to boil semolina or rice in milk in the microwave?
The problem is that milk will boil over, but I wonder if there are some adapted pots for this purpose or if there is some other trick.
You mean semolina or rice pudding? You can certainly make them in the microwave, the trick is simply to use a bowl that's big enough as well as to stop and stir every few minutes. Here's a recipe saying so, including a picture of the plain glass bowl the author used:
Here's another recipe with similar instructions:
You can find tons of other recipes for microwave rice or semolina pudding on Google, repeating pretty much these two points.
If it's boiling over, you're heating it too much. If you were cooking on the stove, you'd be trying to heat it just enough to almost or barely boil; it's quite easy to boil milk over on the stove too. So try using your microwave on its lowest power, or at least reduce it to that power once the milk is nearly boiling. If it still boils over, it's never going to work. If it's not cooking hot enough, then adjust upward as needed. Keep in mind that if you're cooking something which would be stirred on the stove, you'll still need to stir it some, though probably not as much - it's not extremely hot on the bottom like a stove.