chore(docs): update Zephyr documentation (#6581)

docs/integration/os/zephyr.rst

@@ -106,6 +106,7 @@ The pseudo device binding descriptions can be found at:
 - `button input <https://docs.zephyrproject.org/latest/build/dts/api/bindings/input/zephyr,lvgl-button-input.html>`__
 - `pointer input <https://docs.zephyrproject.org/latest/build/dts/api/bindings/input/zephyr,lvgl-pointer-input.html>`__
 - `encoder input <https://docs.zephyrproject.org/latest/build/dts/api/bindings/input/zephyr,lvgl-encoder-input.html>`__
+- `keypad input <https://docs.zephyrproject.org/latest/build/dts/api/bindings/input/zephyr,lvgl-keypad-input.html>`__
 
 Essentially those buffer the :code:`input_event` generated by the device pointed to by the :code:`input` phandle or if left
 empty the binding captures all events regardless of the source. You do not have to instantiate or manage the devices yourself,
@@ -157,6 +158,31 @@ Overlays can be used to enable/disable features for specific boards or build
 targets. For more information refer to the
 `application development guide <https://docs.zephyrproject.org/latest/develop/application/index.html#application-configuration>`__.
 
+Performance Tuning in LVGL
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To optimize LVGL's performance, several `kconfig` options can be configured:
+
+- **CONFIG_LV_Z_VDB_SIZE**: Sets the rendering buffer size as a percentage of the display area, adjustable from 1% to 100%. Larger buffers can enhance performance, especially when used with **CONFIG_LV_Z_FULL_REFRESH**.
+
+- **CONFIG_LV_Z_DOUBLE_VDB**: Enables the use of two rendering buffers, allowing for parallel rendering and data flushing, thus improving responsiveness and reducing latency.
+
+- **CONFIG_LV_Z_VDB_ALIGN**: Ensures that the rendering buffer is properly aligned, which is critical for efficient memory access based on the color depth.
+
+- **CONFIG_LV_Z_VBD_CUSTOM_SECTION**: Allows rendering buffers to be placed in a custom memory section (e.g., `.lvgl_buf`), useful for leveraging specific memory types like tightly coupled or external memory to enhance performance.
+
+Zephyr ≤ 3.7.0 Specific Options
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+For Zephyr versions 3.7.0 and below, additional options are available to manage LVGL's frame flushing:
+
+- **CONFIG_LV_Z_FLUSH_THREAD**: Enables flushing LVGL frames in a separate thread, allowing the main thread to continue rendering the next frame simultaneously. This option can be disabled if the performance gain is not needed.
+
+  - **CONFIG_LV_Z_FLUSH_THREAD_STACK_SIZE**: Specifies the stack size for the flush thread, with a default of 1024 bytes.
+
+  - **CONFIG_LV_Z_FLUSH_THREAD_PRIO**: Sets the priority of the flush thread, with a default priority of 0, indicating cooperative priority.
+
+For newer versions of Zephyr, the OSAL (Operating System Abstraction Layer) can be utilized, which takes care of the flushing.
 
 Where can I find more information?
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