docs(draw): add a short description about each draw unit (#9890)

Co-authored-by: cubic-dev-ai[bot] <191113872+cubic-dev-ai[bot]@users.noreply.github.com>

docs/src/main-modules/draw/draw_pipeline.rst

@@ -87,6 +87,7 @@ capable of performing rendering.
 For a reference implementation of a draw unit, see
 `lv_draw_sw.c <https://github.com/lvgl/lvgl/blob/master/src/draw/sw/lv_draw_sw.c>`_.
 
+Learn more about :ref:`draw units`
 
 Creating Draw Units
 -------------------

docs/src/main-modules/draw/draw_units.rst

@@ -0,0 +1,133 @@
+.. _draw_units:
+
+Draw Units
+==========
+
+A "Draw Unit" (:cpp:type:`lv_draw_unit_t`) is any peripheral or system that can render
+something on the screen. This can be a CPU core, a GPU, a custom rendering library for
+specific draw tasks, or any entity capable of performing rendering.
+
+LVGL supports several built-in draw units that can be enabled in ``lv_conf.h``.
+
+Software Rendering
+******************
+
+A highly optimized renderer written in C. Even when no GPU is enabled, software rendering
+provides a performant, low-footprint, and very capable engine for rendering.
+
+Rendering Features
+------------------
+
+The software renderer is capable of rendering most typical draw tasks, including:
+
+- fill rectangles with a color or gradient
+- rounded rectangles and borders
+- draw box shadows
+- blend, rotate, scale, or recolor images
+- draw labels, even with rotated letters
+- draw skew lines with perpendicular endings and any thickness
+- draw arcs with rounded or straight endings
+- blur an area
+- draw drop shadows for any shape
+- anti-alaising for all rendering
+- and many more
+
+Color Format Support
+--------------------
+
+It also supports the most common color formats as source and destination, such as
+RGB888, XRGB8888, ARGB8888, RGB565, L8, A8, I1, and more.
+
+Multi-Core Rendering
+--------------------
+
+In case of a multi-core system, each core can perform software rendering in parallel by setting
+``LV_DRAW_SW_DRAW_UNIT_CNT`` to greater than ``1``, and setting ``LV_USE_OS``
+to something other than ``LV_OS_NONE``.
+
+Assembly Acceleration
+---------------------
+
+Software rendering can also use various assembly accelerators, such as:
+
+- Arm Neon: available on most Cortex-A cores
+- Arm Helium: available on Cortex-M55 and M85 cores
+- Arm-2D: a complete library supporting highly optimized Helium acceleration
+- RISC-V: uses SIMD instructions on RISC-V cores
+
+These can be enabled in ``lv_conf.h`` and typically provide 10-30% faster rendering.
+
+Vector Graphics
+---------------
+
+To render vector graphics (e.g. SVG), LVGL uses a third-party library called
+`ThorVG <https://github.com/thorvg/thorvg>`_. It supports most vector rendering features such as:
+
+- paths from lines, arcs, and Bézier curves
+- stroke with dashing and joint settings
+- fill with color, image, or gradient
+- and many more
+
+To use it, enable ``LV_USE_THORVG_INTERNAL`` and ``LV_USE_VECTOR_GRAPHIC``.
+
+VG-Lite
+*******
+
+A powerful vector graphics accelerator IP developed by Verisilicon. It is widely used
+by NXP and other chip vendors to provide hardware-accelerated 2D and vector rendering.
+
+Key Features
+------------
+
+- Hardware-accelerated vector path rendering (lines, arcs, Bézier curves)
+- Fill and stroke support with solid colors and gradients
+- Image transformations such as scaling, rotation, and blending
+- Anti-aliasing for smoother edges
+- Efficient memory usage optimized for embedded systems
+- High performance with low CPU utilization
+
+To enable VG-Lite support in LVGL, set ``LV_USE_DRAW_VG_LITE`` in ``lv_conf.h``.
+
+NemaGFX
+*******
+
+NemaGFX is a graphics API and GPU family developed by Think Silicon. It is used in
+various embedded platforms, including STM32 devices with NeoChrom GPUs and Ambiq MCUs,
+to provide hardware-accelerated 2D rendering.
+
+In addition to the 2D engine, some platforms also include NemaVG, which provides
+hardware-accelerated vector graphics rendering.
+
+Key Features
+------------
+
+- Hardware-accelerated 2D rendering (fills, blits, compositing)
+- Image transformations such as scaling, rotation, and blending
+- Alpha blending and transparency support
+- Vector graphics acceleration via NemaVG (paths, fills, strokes)
+- Optimized for low-power embedded systems
+- Offloads rendering from the CPU for improved performance
+
+To enable NemaGFX support in LVGL, set ``LV_USE_DRAW_NEMA_GFX`` in ``lv_conf.h``.
+
+Dave2D
+******
+
+Dave2D is a 2D graphics accelerator developed by TES and widely used on
+Renesas and Alif MCUs.
+
+In Renesas FSP, the DRW peripheral is provided as a port of D/AVE 2D, which is the driver
+used by the LVGL Dave2D draw unit.
+
+Key Features
+------------
+
+- Rectangle drawing, including gradients
+- Image drawing, scaling, and rotation
+- Letter drawing
+- Triangle drawing
+- Line drawing
+- Background rendering that reduces CPU load during drawing
+
+To enable Dave2D support in LVGL, set ``LV_USE_DRAW_DAVE2D`` in ``lv_conf.h``.
+

docs/src/main-modules/draw/index.rst

@@ -11,4 +11,5 @@ Drawing
     draw_api
     draw_layers
     draw_descriptors
+    draw_units
     snapshot