Посмотрите в стартап файле имена обработчиков прерываний и просто создайте функцию с таким именем.
В keil так дело обстоит. Думаю что и в яре тоже как-то так.
Цитата
Writing An Interrupt Handler For Cortex-M3
On Cortex-M3, an interrupt service routine enters and returns in the same way as a normal function, which means no special keywords are required.
In the Interrupt.c file in the Project4CM3 project, the interrupt function UART_Handler is provided. Note that when you add an interrupt function for Cortex-M devices, you must also add the name of that function in the interrupt vector table. You do this in the system startup code cstartup.s. For this tutorial, a reference to the UART_Handler function is already provided in __vector_table, which you can find in the file CstartupCM3.s.
For more information about how to write device-specific interrupt functions for Cortex-M, see the IAR C/C++ Development Guide for ARM®.