transformation help

I have an xml doc in the form of

<doc>
<category>cat 1</category>
<item>item 1</item>
<item>item 2</item>
<category>cat 1</category>
<item>item 3</item>
<item>item 4</item>
<item>item 5</item>
</doc>

and i want to transform it into

<doc>
<category name=3D"cat 1">
<item>item 1</item>
<item>item 2</item>
</category>
<category name=3D"cat 2">
<item>item 3</item>
<item>item 4</item>
<item>item 5</item>
</category>
</doc>

how should i go about this?

Thanks,
Marcus