How to set font per Unicode range / codepoint in fontconfig?

I recently figured out how to use fontconfig on Linux to set system default fonts for serif, sans-serif and monospaced fonts; basically, you save an XML configuration file to ~/.config/fontconfig/fonts.conf with the following content:

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>

<match>
  <test qual="any" name="family"><string>serif</string></test>
  <edit name="family" binding="strong" mode="prepend_first">
    <string>Gentium</string>
    <string>Sun-ExtA</string>
    <string>HanaMinA</string>
    <string>HanaMinB</string>
    </edit>
  </match>

</fontconfig>

The binding="strong" mode="prepend_first" attributes ensure that the matching rules take precedence over other settings, and the sequence of font names ensure that where a font doesn't contain a given code point / character, the next font in the list is tried (this list applies top-to-bottom; IMHO it should really be a later-binds-stronger logic, but whatever).

The great thing about this configuration is that it works in text editors and terminal emulators alike.

However, there's still a nag: there are many cases where a given font does contain a given glyph, but another font would be preferrable for that codepoint; for example, Sun-ExtA is a great default font for CJK characters, but it also covers lots and lots of non-CJK characters and has a few problematic glyphs.

Suppose I don't like the appearance of 〇 U+3007 IDEOGRAPHIC NUMBER ZERO in Sun-ExtA and would rather use HanaMinA for it, how could I do that with fontconfig? Obviously I can't just prioritize the entry for HanaMinA over Sun-ExtA, as that would affect all of the glyphs that are contained in both fonts.

My hunch is that there should be a solution involving elements <charset> (according to the fontconfig user documentation, "This element holds at least one element of an Unicode code point or more") and/or <range> ("This element holds the two elements of a range representation"—presumably to denote a range of Unicode code points). I couldn't find a single example how to use these elements, though.

Is it possible to configure fontconfig to use a specific font for a single Unicode code point or a range of codepoints?