I looked at "K20 Sub-Family Reference Manual". There are two USB modules here :
- Universal Serial Bus OTG Controller (USBOTG) ;
- USB High Speed OTG Controller (USBHS).
As I see, the USBHS is ARC IP based and it is very similar to i.MX6 OTG, at least,
so called USB-Core Registers. Note, the i.MX6 OTG also has so called non-core
(USB) registers, which are Freescale specific.
So, there is ARC USB core part of USB modules of i.MX6 and Kinetis which is practically
the same for both ones, but some specific registers also may be found.
As for the USB Stack, the i.MX6 is not supported there (I think because of the mentioned specifics).