This commit enables the microphone mute button and the screen rotate button, even if the latter is improperly linked. I have documented how to achieve this in https://wiki.archlinux.org/index.php/MSI_P15#Fn_Keys .
evdev:atkbd:dmi:bvn*:bvr*:bd*:svnMICRO-STAR*:pnU90/U100:*
KEYBOARD_KEY_e4=reserved
+# MSI Prestige15 A10SC specific keycodes. Needed for microphone and screen rotation
+evdev:atkbd:dmi:bvn*:bvr*:bd*:svnMicro-Star*:pn*A10SC*:pvr*
+ KEYBOARD_KEY_f1=f20
+ KEYBOARD_KEY_f2=f21
+
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# MSI
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