Either:

• one or more 'glyphRef' elements, or
• one or more 'altGlyphItem' elements.

One or more 'glyphRef' elements. Any number of descriptive elements and at most one 'mpath' element, in any order. Any number of descriptive elements and exactly one light source element, in any order. Any number of descriptive elements and exactly one light source element, in any order. Any number of descriptive elements and at most one 'font-face-src' element, in any order. rootmost ‘svg’ element