GCC macro

Very good reference:

http://gcc.gnu.org/onlinedocs/gcc-3.1.1/cpp/Macros.html#Macros

#define __IRQ_SYSTMR(_X) IRQ_TMR ## _X
#define _IRQ_SYSTMR(_X) __IRQ_SYSTMR(_X)
#define IRQ_SYSTMR _IRQ_SYSTMR(CONFIG_IPIPE_SYS_TIMER)

#ifdef CONFIG_BF533
#define __IRQ_PRIOTMR(_X) CONFIG_TIMER ## _X
#else
#define __IRQ_PRIOTMR(_X) CONFIG_IRQ_TMR ## _X