For Firefox, you must use the plugin "XHTML Ruby Support" (
https://addons.mozilla.org/en-US/firefox/addon/1935)
For IE, it work natively.
As I know, don't work with WebKit based browser (Google chrome and Safari), but I don't know if there is any plugin.
For examples (and test in you browser) look at this page:
http://www.w3.org/International/tests/sec-ruby-markup-1
The example with the parenthesis (as the <rp> value) is in the point "3 Simple ruby, short, wide-cell ruby text".
Of course, you need to be able to see Japanese characters in your computer to see it properly.
Try this code in your wiki (or dokuwiki playground)
<html><ruby>
<rb>Normal text</rb>
<rp>(</rp>
<rt>Ruby text</rt>
<rp>)</rp>
</ruby>
</html>
If your browser render the ruby, you will see "Normal text" with a small "Ruby text" over.
If it did not work you will see "Normal text (Ruby text)"