OpenVG for the uninitiated is a 2D vector graphics API backed by The Khronos Group. It hasn't been updated in almost one decade with OpenGL ES largely taking over on the mobile/embedded front, but there still is some embedded hardware out there with still having OpenVG v1.1 drivers. There used to be an OpenVG state tracker in Mesa's Gallium3D, but that's long been dead.
The Qt Company has added OpenVG acceleration now for helping out embedded devices lacking OpenGL 2.0 support but managing to have EGL+OpenVG capabilities compared to the status quo of having only software acceleration on those platforms. Qt still insists that OpenVG has relevancy today, "A few examples of system-on-chips with this configuration are the NXP iMX6 SoloLite, and Vybrid VF5xxR chips which both use the GC355 Vector GPUs enabling OpenVG. The OpenVG working group may no longer be actively working on the standard itself, but SoC vendors are still releasing on hardware that supports OpenVG."
More details on the OpenVG support coming to Qt 5.9 can be found via today's Qt.io blog post. Other Qt 5.9 tool-kit features are covered in this earlier article.