As described within the Intel QST SDK and its programmer reference manual, Quiet System Technology is described as:
The Intel Management Engine (ME) hosts a firmware subsystem – Intel Quiet System Technology (QST) – that provides support for the monitoring of temperature, voltage, current and fan speed sensors that are provided within the Chipset, the Processor and other devices on the Motherboard. For each sensor, a Health Status, based upon established thresholds, will be determined at regular intervals. Intel QST also provides support for acoustically-optimized fan speed control. Based upon readings obtained from the temperature sensors, Intel QST will determine, over time, the optimal speeds at which to operate the available cooling fans, in order to address existing thermal conditions with the lowest possible acoustic impact.Intel's Software Development Kit provides Linux support for the QST sample application, but there hasn't been a mainline Linux kernel hwmon driver for this technology that's found within modern Intel chipsets.
Earlier this year there was early support for Intel QST in LM_Sensors while being announced now is a new Intel QST driver for Linux. The code for this new Quiet System Technology driver is currently on GitHub.
Hopefully this new Linux Intel hardware sensor driver will be merged eventually into the mainline Linux kernel. Unfortunately, some work is still needed - the driver was written against the old Linux 2.6.39 kernel, only QST 1.0 is implemented and not the QST 2.0 support found in newer Intel hardware, and there isn't yet any PWM (Pulse Width Modulation) methods implemented.