A voltage divider will be a very bad design approach. Because the voltage level will vary depending on the load that you are planning to use (micro-controller in your case). So depending on the current drawn by the controller and also the state of IO pins the voltage will keep on varying.
If you are looking for some cheap options then 3.3V zener will also work (assuming you are not looking for tight regulation, which seems to be case in your case)
Else you can go for packaged IC's like LD1117 which has input voltage limit up to 15V. But you have to calculate potential maximum current drawn by the controller and hence heat dissipation across the regulator (you may have to use heatsink as well, which might defeat the purpose of using it on first place).