Socialdarwinist

To add a new layout to your system, an example is how I added the pan-Cyrillic keyboard layout – I appended /usr/share/X11/xkb/symbols/ru by it, and as I wanted to use capslock as a fifth-level-modifier, which strangely nobody had defined until then, I included the given definition for the capslock key as fifth-level modifier in the /usr/share/X11/xkb/symbols/level5 file.
For registering the pan-Cyrillic keyboard layout, I had to include the listed XML data for the files /usr/share/X11/xkb/rules/base.extras.xml and /usr/share/X11/xkb/rules/evdev.extras.xml as a variant under the “ru” layout, that is to say nested in its <variantList> element.
Currently there is no way to add keyboard layouts without manipulating package-controlled system files, so you have to repeat these steps after each reinstallation of the X keyboard configuration files (written by the package xkeyboard-config on Arch Linux and derivates).
For this specific keyboard layout presented here this is not necessary since I contributed the layou

Socialdarwinist

default  partial alphanumeric_keys
xkb_symbols "basic" {

    name[Group1]= "Arabic";

    key.type[Group1]="FOUR_LEVEL";
    
    key <TLDE> {  [     Arabic_thal,        Arabic_shadda,            Arabic_percent,               U0609 ]};  // ‎ذ‎ ‎◌ّ‎     ‎٪‎ ‎؉‎
    key <AE01> {  [               1,               exclam,                  Arabic_1,            NoSymbol ]};  // 1 !     ١
    key <AE02> {  [               2,                   at,                  Arabic_2,            NoSymbol ]};  // 2 @     ٢

Socialdarwinist

	<layout>
		<configItem>
			<name>trans</name>
			<description>International Phonetic Alphabet</description>
		</configItem>
		<variantList/>
	</layout>