To get an own ActionController that can be called like this:

http://www.mysexydomain.de/nicefrontname/nicecontrollerprefix/niceactionprefix/

… you have to add the following snippet into the FE or BE section of your config.xml:

<frontend>
	<routers>
		<sns_documentmaster>
			<use>standard</use>
			<args>
				    <module>SNS_Documentmaster</module>
				    <frontName>nicefrontname</frontName>
			</args>
		</sns_documentmaster>
	</routers>
</frontend>