UDC

There is a USB client on handheld Vita devices. It uses a proprietary multi-connector on the OLED (PCH-1XXX) units and a micro-USB on the LCD (PCH-2XXX) units.

PCH-1XXX Pinout

Because of the existence of the USB ethernet adaptor, that means there exists a way to use the port in host mode probably through USB OTG or something similar.

Teardown of Vita OLED dock here.

Pin	Name	Description
1	Power?	No known use (N/C on cables, USB ethernet), goes to SN99057 pins 31-32
2	Power?	Same net as pin 1
3	Analog Ground (TRRS Pin 3)	For stereo output
4	Right Channel Audio (TRRS Pin 2)	To audio codec IC
5	Left Channel Audio (TRRS Pin 1)	To audio codec IC
6	UART RX	See UART Console
7	UART TX	See UART Console
8	UART CTS	See UART Console
9	UART RTS	See UART Console
10	Audio?	To audio codec IC, not seen used anywhere.
11	Accessory Enable?	Digital signal. Pull-down to GND on dock. To Syscon (C11), connected on USB Ethernet
12	TRRS Pin 4	Digital signal. To Syscon (F9), connected on USB Ethernet
13	?	To Syscon (G4), not seen used anywhere.
14	GND 1	GND on Vita and USB ethernet adapter, N/C on charging cable and dock
15	?Peripheral Detect?	To large ceramic chip, 125K pull-down
16	GND 2	GND on Vita, N/C on USB ethernet and charging cable, small cap to GND on dock
17	VCC	+5V VDC
18	VCC	Same net as pin 17
19	GND 3	GND on Vita and charging cable, N/C on USB ethernet, large cap to GND on dock
20	D-	USB Data
21	D+	USB Data

PCH-2XXX Pinout

Port is a standard micro-USB Type B. Highly likely that USB OTG is supported in hardware although there's no evidence that it's enabled in software.

Pin	Name	Description
1	VCC	+5V VDC
2	D+	USB Data
3	D-	USB Data
4	ID	USB OTG
5	GND	Ground