CMSIS is a Cortex M Software interface standard while mbed is an operating system of which CMSIS is a low level component.
Your platform implementation uses CMSIS API’s eg: to register / enable / disable interrupts, remap etc…
Please see following git:
This has cmsis-core implementation.
Below it into the git there are other platform’s using cmsis-core
Click on any of them and you will see NVIC_EnableIRQ and other API’s of cmsis-core are being used.
eg: cmsis-core-k64f/system_MK64F12.c at master · ARMmbed/cmsis-core-k64f · GitHub
As per my understanding I don’t thing you might need to port cmsis package, but you will have to use the package/module into your system
Thanks & BR,