Symfony2: define web path in kernel

I would like to define path to my custom /uploads directory in /web/bundles/index. I would like to call it the same or similar way the getRootDir() is called through the kernel.

I need that so in the future when I rename /web directory name to /public_html I wouldn't have to change it in many files, just one (i.e. config.yml).

What is the best practice and what would you suggest?