Render parts of a QML scene to offscreen buffer (FBO)

Anyone know of a way to render parts of a QML scene (perhaps subtrees of the scene graph) to an offscreen buffer, like an FBO? Something similar to this: https://bugreports.qt-project.org/browse/QTBUG-19171 Specifically, my use case is that I want to render a component within the scene and all of its children to a separate buffer so that I can recomposite it manually. Performance is of little concern. That is, I don’t mind if the UI is interrupted for a long time while the offscreen rendering occurs. After reading the scene graph documentation and API, it seems like I might have to implement a custom scene graph renderer or get the subtree from the component via its QQuickItem::updatePaintNode method and somehow render this subtree manually to an FBO. Just not sure what’s the best way to go about this. Any advice would be appreciated!