How to use existing hook in twentytwelve to all theme of wordpress?

I Recently tried to read the tutorial for wp_footer and also twentytwelve_credits for creating a sample wordpress plugins.
wp_footer hook to display the footer beneath the page area.
twentytwelve_credits hook display the footer in the page footer on a white background.
**For Example:**
I tried this code to show the footer with custom message.

[ Moderator note: please wrap code or log lines in backticks or use the code button. ]

<?php
    function your_function() {
        echo '<p>This is inserted at the bottom</p>';
    }
    add_action('wp_footer', 'your_function');
    ?>

I tried this code after switching a theme to twenty twelve.

<?php
    function your_function() {
        echo '<p>This is inserted at the bottom</p>';
    }
    add_action('twentytwelve_credits', 'your_function');
    ?>

I find the difference when using different hooks. wp_footer hook is working for all themes but it is in bottom of the site. twentytwelve_credits is working for the twentytwelve theme only. I beleive twentytwelve_credits is the efficient way rather than wp_footer. but its hard to change the hook for every theme. I am not sure is the way to show of the footer with every theme with twentytwelve_credits. Any Possibilities like do_action('twentytwelve_credits');.
Any Suggestion would be great.