Hello,
Unfortunately there is no documentation and I can't recommend you how to put FreeRTOS on layerscape processors because they are designed to be used with Linux.
On the other hand, we have the Real-Time Edge Software, it enables real-time applications for the i.MX and Layerscape products and can be easily integrated with the Yocto Project SDKs for these products. Real-time edge software enables real-time capabilities via support for Preempt-RT Linux® for low latency applications, baremetal framework and support for real-time operating system (RTOS) on the Arm® Cortex®-A or Cortex®-M cores.