Hello everyone.

I am facing issues when trying to use UART3 and UART4 of the STM32F091 (they were not available at the original DTS, I had to include them). I have noticed that these UARTs share the same interrupt number 29. When both are enabled I can send no data to them. Any clue?

I will try to do a pull request after solving the problem. 

Thank you.

Best regards,