* mcast: Join or leave a multicast group (for TFTP) - optional
* write_hwaddr: Write a MAC address to the hardware (used to pass it to Linux
* on some platforms like ARM). This function expects the
- * eth_pdata::enetaddr field to be populated - optional
+ * eth_pdata::enetaddr field to be populated. The method can
+ * return -ENOSYS to indicate that this is not implemented for
+ this hardware - optional.
* read_rom_hwaddr: Some devices have a backup of the MAC address stored in a
* ROM on the board. This is how the driver should expose it
* to the network stack. This function should fill in the