Relogo allows you to easily add support for the rel="logo" spec as described at relogo.org.
Relogo lets you easily add support for the rel=”logo” tag to your site. It operates in accordance with the specification published on relogo.org.
Using this plugin you can easily add the tag to your site without having to edit any code, and without needing to change your theme’s files. Just provide the URL for your logo’s SVG file, and you’re done.