Asterisk 13.8.0 to 13.9.1 Upgrade on ARM, with FreePBX 13.0.143 GUI

Hello all,
I had compiled and installed Asterisk 13.0.8 and FreePBX 13.2.x on an Ubuntu 15.10 Linux running on ARM based SoC called “Colibri T30” from Toradex Company.

All are good and Asterisk and FreePBX are working fine on my system.
However, I need to upgrade the current installed Asterisk version 13.8.0 to the available latest version 13.9.1 but I do not know how should I really do to upgrade it safely.
I do not know if I can just download the latest source and compile it as usual or need to do anything else.
For example, it’s not clear for me if I need to reinstall the FreePBX as well or just Asterisk compile and install will be sufficient.
My Server is Production server and I do not want to break anything.

Do you guys have any idea what is the best practice to upgrade an existing Asterisk combined with FreePBX GUI to the latest version of Asterisk?

Your help will be much appreciated.