Using the interrupt manager insures that RTEMS knows
when a directive is being called from an ISR. The ISR may then
use system calls to synchronize itself with an application task.
The synchronization may involve messages, events or signals
being passed by the ISR to the desired task. Directives invoked
by an ISR must operate only on objects which reside on the local
node. The following is a list of RTEMS system calls that may be
made from an ISR: