PBP (PPP) docking deck detailed spec

[Rosbeefandino]

where can i find complete specification of this product?
i want it to work well with my ppp and mobian.
i 'm not a good developper but want to practice to firmware and driver development .
but first i think i need good understanding of this hardware.

for now i clarify the structure of usb tree :
usbA ports numbered from vga port to sdcar reader A1,A2,A3
linux bus 5
 -> Vialab usb2 hub 4ports Vendor=2109 ProdID=2817
    -> port1 directly connected to physical port A2
    -> port2 directly connected to physical port A1
    -> port3 ?
    -> port4 conected to Terminus hub 4 ports Vendor=1a40 ProdID=0801
        -> port1 directly connected to physical port A3
        -> port2 ?
        -> port3 ?
        -> port4 terminus hub 4p Vendor=1a40 ProdID=0801
            ->port1 directly connected to physical SDcard port
            ->port2 directly connected to physical microSD port
            ->port3 fresco logic ( it6564?) hdmi/vga convertor Vendor=1d5c ProdID=7102
                            ^seems to have a firmware is it possible to flash ?
            ->port4 CMX sound card conected to audio jack Vendor=2000 ProdID=dd00

linux bus 6
 -> vialab usb3 hub 4p
    -> port1 ?
    -> port2 ?
    -> port3 eth adapter rtl8153 0bda:8153
    -> port4 ?

how i named the ports ; from left to right facing the ports
jack, sdcard/microsdcard, usbc 2, usbc 1, usba 3, usba2, usba1, vga, hdmi, usbc pd Femal, usbc pd male.

i don't know where shoud be mentioned the sound card to send audio thrue the HDMI. is it an interface of the it6564.
maybe it required to send specific encoded sound to specific it6564 interface?

is anyone have a photo of the interior of the docking station ?