Hi Customer,
You don't need to port it by yourself, because we already have the FreeRTOS code in the KSDK for MK22 chip.
Please download the SDK code from this link:
Welcome | MCUXpresso SDK Builder
Select the chip which you want, then note the following steps:

Select the FreeRTOS, then download the code.
You can find the freeRTOS code in folder:
SDK_2.3.1_FRDM-K22F\boards\frdmk22f\rtos_examples
Wish it helps you!
Have a great day,
Kerry
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