On the default device tree, the MCA UART that's connected to the
XBee socket is enabled. This registers as ttyMCA0.
Add a udev rule for this path so that ModemManager checks for
modems in this serial port.
Signed-off-by: Hector Palacios <hector.palacios@digi.com>
https://jira.digi.com/browse/DEL-6366