FreeRTOS for Atmel's SAM Cortex-M3 Switch between tasks
Send the task a signal, or notification, as FreeRTOS calls then.

But, you most likely wrote some interrupt layer now. You probably use queues or buffers to send the data to the task. Your task can also wait for the queue to contain data.
The queue code will contain the necessary flags to set the task pending.

Yield is something else in OS context. It basically means the task ends its given cpu time-slice early. So the next task is switched in. But this could very well be the same task if the design is poor.