Get serial devices working on Synology DS216+II DiskStation

Hello

I have also a DS216Play. When I plug my USB-to-Serial adapter based on PL2303 chip, I can see it in the info center of DSM.
If I use the SSH to search the port of it, I see nothing. No ttyUSB0 or ttyACM0.
I didn’t find on google what is going on.

|__usb1 1d6b:0002:0310 09 2.00 480MBit/s 0mA 1IF (ehci_hcd ehci-platform.0) hub
|__usb2 1d6b:0001:0310 09 1.10 12MBit/s 0mA 1IF (Linux 3.10.105 ohci_hcd Generic Platform OHCI Controller ohci-platform.0) hub
|__2-1 067b:2303:0300 00 2.00 12MBit/s 100mA 1IF (Prolific Technology Inc. USB-Serial Controller c6a3cfa3ccbecaa4cb88a8c4a5ccbedb)
|__usb3 1d6b:0002:0310 09 2.00 480MBit/s 0mA 1IF (Linux 3.10.105 xhci-hcd xHCI Host Controller xhci-hcd.0.auto) hub
|__usb4 1d6b:0003:0310 09 3.00 5000MBit/s 0mA 1IF (Linux 3.10.105 xhci-hcd xHCI Host Controller xhci-hcd.0.auto) hub

Any suggestions ?

Tx

Antoine