How can I rotate svg <tspan> element ?

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How can I rotate svg <tspan> element to vertical mode?
I want to rotate vertical mode two

<tspan>

element from

<text>

element.

my sample -

<svg xmlns="http://www.w3.org/2000/svg"
     xmlns:xlink="http://www.w3.org/1999/xlink">
    <text y="10">
        <tspan x="10">Vertical Text (up 2 down mode)</tspan>
        <tspan x="20">Vertical Text (down 2 up mode)</tspan>
    </text>
</svg>

Sample Image for SVG Design

Thank you,
MinChanSike