<svg xmlns="http://www.w3.org/2000/svg">
<symbol id="gamecontroller" viewBox="0 0 64 64"> ... </symbol>
<symbol id="icons-11" viewBox="0 0 65 65"> ... </symbol>
</svg>
.my-icon {
display: inline-block;
vertical-align: middle;
width: 100px;
height: 100px;
background: url('svg-symbols.svg#gamecontroller') no-repeat;
background-size: contain;
}
<svg xmlns="http://www.w3.org/2000/svg">
<symbol id="gamecontroller" viewBox="0 0 64 64"> ... </symbol>
<symbol id="icons-11" viewBox="0 0 65 65"> ... </symbol>
<use xlink:href='#gamecontroller' />
</svg>