Mobile High-Definition Link (MHL)
Mobile High-Definition Link is an industry standard for a mobile audio/video interface that allows you to connect mobile phones, tablets and other portable (CE) devices to your TV and give you more options than just your standard HDMI connection. HDMI is not generally intended to be used as a power supply, unless the port is marked as an MHL port. Then it can provide 5 volts to charge mobile devices while they are connected to the display; the current is 500mA for MHL 1 and 900mA for MHL 2 and 3.
On ports that are not marked as MHL ports, the supply is not expected to be more than 10mA, and this is mostly used for hotplug detection, although it can also feed things like format converters and inline amplifiers for long cable runs.