Hi John,
There is not an API to do what you want. However, you maybe could try this:
ENET_CONTEXT_STRUCT_PTR enet_ptr = NULL;
enet_ptr = _mqx_get_io_component_handle(IO_ENET_COMPONENT);
enet_ptr->PARAM_PTR = &ENET_default_params[0];
(*param_ptr->ENET_IF->MAC_IF->PHY_WRITE)(enet_ptr, reg_index, data, timeout);
For more reference, I came out with the adobe code based on the ENET_initialize_ex() function. I didn't tested so you will need to check and see if compiles and works. I hope this helps you.
Best Regards,
Garabo