Can the C0/C4/C5(PCIE group) be configured as Endpoint?

The Xavier OEM explains that the C0/C4/C5 can be configured as Endpoint.
but in the document NVIDIA Jetson AGX Xavier Series PCIe Endpoint Design Guidelines, there is a description that " A Jetson AGX Xavier configured as an Endpoint can connect to another configured as Root Port. Endpoint support is only possible on the PCIe Controller C5 (x8)".
so i wonder that if the C0/C4 can be configured as an Endpints?

Hardware capability-wise, both C0 and C4 (along with C5) support operating in the endpoint mode. But, required PCB level support is not present in Jetson AGX Xavier.

sorry,i do not get the point,PCB level support?

I mean, the REFCLK configuration required to operate C0 and C4 in the endpoint mode is not present at the board level. So, they can’t be operated in the endpoint mode.

Thanks for reply