Complex providers structure in one hwnd-control

Hello, I have 1 hwnd-control, but I want it to appear in such structure: base-root-element -> root-elements -> simple-elements.

base-root-element is a menu (imp. FragmentRoot, ProviderFragment, ProviderSimple)
root-elements are groups (imp. FragmentRoot, ProviderFragment, ProviderSimple)
simple-elements are menuItems (imp. ProviderFragment, ProviderSimple)

I have a problem: what I must return in get_HostRawElementProvider in root-elements (groups)? This provider implements areIRawElementProviderFragmentRoots, but they have no hwnd-control (so, I can not use UiaHostProviderFromHwnd), and it can not return NULL.

May be someone have an example of implementing such providers-structure in one hwnd-control?