Hi Marcos:
OSA_SemaCreate(), OSA_SemaWait() or OSA_SemaPost() are in OS abstraction layer, it is designed and implemented for supported RTOS to provide a common set of service routines for drivers, integrated software solution, and upper-level applications so that a common code base can be used regardless of the target OS.
You can find the sample code in KSDK1.3, for example.
platform/drivers/src/flexio
For the new KSDK 2.x version, OSA is no longer required. So I would recommend you start directly the FreeRTOS API, for example xSemaphoreTake, xSemaphoreGive, xSemphoreCreateBinary
Regards
Daniel