Raspberry PI 3 B / B+ How to Enable UART & interface with GSM HD

This video describes how to enable UART on GPIO pins of RASPBERRY PI 3 B or B+ & to interface with GSM The port /dev/ttyAMA0 in PI 3 is allotted to Bluetooth hardware. port /ttyS0 ,mini uart is allotted to serialport which has to be enabled manually. https://alselectro.wordpress.com/2018/07/25/raspberry-pi-b-b-how-to-enable-uart-interface-with-gsm/