media: docs: add glossary.rst with common terms used at V4L2 spec

Add a glossary of terms used within the media userspace API
documentation, as several concepts are complex enough to cause
misunderstandings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/userspace-api/media/glossary.rst

+.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
+
+========
+Glossary
+========
+
+.. note::
+
+   The goal of this section is to standardize the terms used within the media
+   userspace API documentation. This is Work In Progress.
+
+.. Please keep the glossary entries in alphabetical order
+
+.. glossary::
+
+    Bridge Driver
+	A :term:`device driver` that implements the main logic to talk with
+	media hardware.
+
+    CEC API
+	**Consumer Electronics Control API**
+
+	An API designed to receive and transmit data via an HDMI
+	CEC interface.
+
+	See :ref:`cec`.
+
+    Device Driver
+	Part of the Linux Kernel that implements support for a hardware
+	component.
+
+    Device Node
+	A character device node in the file system used to control and
+	transfer data in and out of a Kernel driver.
+
+    Digital TV API
+	**Previously known as DVB API**
+
+	An API designed to control a subset of the :term:`Media Hardware`
+	that implements	digital TV (e. g. DVB, ATSC, ISDB, etc).
+
+	See :ref:`dvbapi`.
+
+    DSP
+        **Digital Signal Processor**
+
+	A specialized :term:`Microprocessor`, with its architecture
+	optimized for the operational needs of digital signal processing.
+
+    FPGA
+	**Field-programmable Gate Array**
+
+	An :term:`IC` circuit designed to be configured by a customer or
+	a designer after manufacturing.
+
+	See https://en.wikipedia.org/wiki/Field-programmable_gate_array.
+
+    Hardware Component
+	A subset of the :term:`media hardware`. For example an :term:`I²C` or
+	:term:`SPI` device, or an :term:`IP block` inside an
+	:term:`SoC` or :term:`FPGA`.
+
+    Hardware Peripheral
+	A group of :term:`hardware components <hardware component>` that
+	together make a larger user-facing functional peripheral. For
+	instance, the :term:`SoC` :term:`ISP` :term:`IP block <ip block>`
+	and the external camera sensors together make a camera hardware
+	peripheral.
+
+	Also known as :term:`peripheral`.
+
+    I²C
+	**Inter-Integrated Circuit**
+
+	A  multi-master, multi-slave, packet switched, single-ended,
+	serial computer bus used to control some hardware components
+	like sub-device hardware components.
+
+	See http://www.nxp.com/docs/en/user-guide/UM10204.pdf.
+
+    IC
+	**Integrated circuit**
+
+	A set of electronic circuits on one small flat piece of
+	semiconductor material, normally silicon.
+
+	Also known as chip.
+
+    IP Block
+	**Intellectual property core**
+
+	In electronic design a semiconductor intellectual property core,
+	is a reusable unit of logic, cell, or integrated circuit layout
+	design that is the intellectual property of one party.
+	IP Blocks may be licensed to another party or can be owned
+	and used by a single party alone.
+
+	See https://en.wikipedia.org/wiki/Semiconductor_intellectual_property_core).
+
+    ISP
+	**Image Signal Processor**
+
+	A specialized processor that implements a set of algorithms for
+	processing image data. ISPs may implement algorithms for lens
+	shading correction, demosaicing, scaling and pixel format conversion
+	as well as produce statistics for the use of the control
+	algorithms (e.g. automatic exposure, white balance and focus).
+
+    Media API
+	A set of userspace APIs used to control the media hardware. It is
+	composed by:
+
+	  - :term:`CEC API`;
+	  - :term:`Digital TV API`;
+	  - :term:`MC API`;
+	  - :term:`RC API`; and
+	  - :term:`V4L2 API`.
+
+	See :doc:`index`.
+
+    MC API
+	**Media Controller API**
+
+	An API designed to expose and control the relationships between
+	multimedia devices and sub-devices.
+
+	See :ref:`media_controller`.
+
+    MC-centric
+	:term:`V4L2 hardware` device driver that requires :term:`MC API`.
+
+	Such drivers have ``V4L2_CAP_IO_MC`` device_caps field set
+	(see :ref:`VIDIOC_QUERYCAP`).
+
+	See :ref:`v4l2_hardware_control` for more details.
+
+    Media Hardware
+	Subset of the hardware that is supported by the Linux Media API.
+
+	This includes audio and video capture and playback hardware,
+	digital and analog TV, camera sensors, ISPs, remote controllers,
+	codecs, HDMI Consumer Electronics Control, HDMI capture, etc.
+
+    Microprocessor
+	Electronic circuitry that carries out the instructions of a
+	computer program by performing the basic arithmetic, logical,
+	control and input/output (I/O) operations specified by the
+	instructions on a single integrated circuit.
+
+    Peripheral
+	The same as :term:`hardware peripheral`.
+
+    RC API
+	**Remote Controller API**
+
+	An API designed to receive and transmit data from remote
+	controllers.
+
+	See :ref:`remote_controllers`.
+
+    SMBus
+	A subset of I²C, which defines a stricter usage of the bus.
+
+    SPI
+	**Serial Peripheral Interface Bus**
+
+	Synchronous serial communication interface specification used for
+	short distance communication, primarily in embedded systems.
+
+    SoC
+	**System on a Chip**
+
+	An integrated circuit that integrates all components of a computer
+	or other electronic systems.
+
+    V4L2 API
+	**V4L2 userspace API**
+
+	The userspace API defined in :ref:`v4l2spec`, which is used to
+	control a V4L2 hardware.
+
+    V4L2 Device Node
+	A :term:`device node` that is associated to a V4L driver.
+
+	The V4L2 device node naming is specified at :ref:`v4l2_device_naming`.
+
+    V4L2 Hardware
+	Part of the media hardware which is supported by the :term:`V4L2 API`.
+
+    V4L2 Sub-device
+	V4L2 hardware components that aren't controlled by a
+	:term:`bridge driver`. See :ref:`subdev`.
+
+    Video-node-centric
+	V4L2 device driver that doesn't require a media controller to be used.
+
+	Such drivers have the ``V4L2_CAP_IO_MC`` device_caps field unset
+	(see :ref:`VIDIOC_QUERYCAP`).
+
+    V4L2 Sub-device API
+	Part of the :term:`V4L2 API` which control
+	:term:`V4L2 sub-devices <V4L2 Sub-device>`, like sensors,
+	HDMI receivers, scalers, deinterlacers.
+
+	See :ref:`v4l2_hardware_control` for more details.

Documentation/userspace-api/media/index.rst

@@ -35,6 +35,9 @@ Please see:
     mediactl/media-controller
     cec/cec-api
     gen-errors
+
+    glossary
+
     fdl-appendix
 
     drivers/index