[PATCH v2 05/15] media: microchip-isc: add driver documentation

[Balakrishnan Sambath <balakrishnan.s@microchip.com>]

Document V4L2 controls and pipeline modes for ISC/XISC camera interface
on SAMA5D2, SAMA7G5, and SAM9X7.

Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
---
 .../userspace-api/media/drivers/index.rst     |  1 +
 .../media/drivers/microchip-isc.rst           | 71 +++++++++++++++++++
 MAINTAINERS                                   |  1 +
 3 files changed, 73 insertions(+)
 create mode 100644 Documentation/userspace-api/media/drivers/microchip-isc.rst

diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
index 02967c9b18d6..65ef6ba3523e 100644
--- a/Documentation/userspace-api/media/drivers/index.rst
+++ b/Documentation/userspace-api/media/drivers/index.rst
@@ -34,6 +34,7 @@ For more details see the file COPYING in the source distribution of Linux.
 	imx-uapi
 	mali-c55
 	max2175
+	microchip-isc
 	npcm-video
 	omap3isp-uapi
 	thp7312
diff --git a/Documentation/userspace-api/media/drivers/microchip-isc.rst b/Documentation/userspace-api/media/drivers/microchip-isc.rst
new file mode 100644
index 000000000000..2a436fd19272
--- /dev/null
+++ b/Documentation/userspace-api/media/drivers/microchip-isc.rst
@@ -0,0 +1,71 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Microchip ISC/XISC Driver
+=========================
+
+The Image Sensor Controller (ISC) on SAMA5D2 and eXtended ISC (XISC) on
+SAMA7G5/SAM9X7 provide camera capture with hardware image processing.
+
+Supported Hardware
+------------------
+
+==========  ==========  ==============  ================  ===============
+SoC         Controller  Max Resolution  Interface         Hue/Saturation
+==========  ==========  ==============  ================  ===============
+SAMA5D2     ISC         2592x1944       12-bit parallel   No
+SAMA7G5     XISC        3264x2464       12-bit + CSI-2    Yes
+SAM9X7      XISC        2560x1920       12-bit + CSI-2    Yes
+==========  ==========  ==============  ================  ===============
+
+SAM9X7 shares the XISC pipeline with SAMA7G5 but has a smaller internal
+line buffer, limiting horizontal resolution to 2560 pixels.
+
+Controls
+--------
+
+Standard V4L2 controls:
+
+* ``V4L2_CID_BRIGHTNESS``: -1024..1023, default 0
+* ``V4L2_CID_CONTRAST``: -2048..2047, default 256 (1.0x)
+* ``V4L2_CID_GAMMA``: 0..2 selects curve (0=2.4, 1=2.2, 2=1.8)
+* ``V4L2_CID_AUTO_WHITE_BALANCE``: Enable kernel Grey World AWB
+* ``V4L2_CID_DO_WHITE_BALANCE``: Trigger one-shot AWB
+
+SAMA7G5/SAM9X7 add:
+
+* ``V4L2_CID_HUE``: -180..180 degrees
+* ``V4L2_CID_SATURATION``: 0..255, default 16
+
+Custom controls (defined in ``atmel-isc-media.h``):
+
+* ``ISC_CID_R_GAIN``, ``ISC_CID_B_GAIN``, ``ISC_CID_GR_GAIN``,
+  ``ISC_CID_GB_GAIN``: WB gains, 0..8191, Q2.9 (512 = 1.0x)
+* ``ISC_CID_R_OFFSET``, ``ISC_CID_B_OFFSET``, ``ISC_CID_GR_OFFSET``,
+  ``ISC_CID_GB_OFFSET``: WB offsets, -4096..4095
+* ``ISC_CID_CC_RR`` ... ``ISC_CID_CC_BB``: 3x3 color correction matrix,
+  signed Q4.8 (256 = 1.0)
+* ``ISC_CID_CC_OR``, ``ISC_CID_CC_OG``, ``ISC_CID_CC_OB``: RGB offsets
+* ``ISC_CID_GAMMA_R_LUT``, ``ISC_CID_GAMMA_G_LUT``,
+  ``ISC_CID_GAMMA_B_LUT``: Per-channel gamma LUTs, 64-entry arrays
+
+Pipeline
+--------
+
+Pipeline modules: DPC -> WB -> CFA -> CC -> GAM -> CBHS/CBC -> CSC -> SUB
+
+* DPC: Defective Pixel Correction (XISC only), black level subtraction
+  to sensor bit depth, green disparity correction
+* WB: White Balance gains/offsets
+* CFA: Color Filter Array interpolation (demosaic)
+* CC: Color Correction matrix
+* GAM: Gamma correction (preset or per-channel LUT)
+* CBHS: Contrast/Brightness/Hue/Saturation (XISC only)
+* CBC: Contrast/Brightness (ISC only)
+* CSC: Color Space Conversion (RGB to YCbCr)
+* SUB: Chroma subsampling (4:2:2, 4:2:0)
+
+Pipeline usage depends on input and output formats:
+
+* Raw Bayer input, RGB output: DPC, WB, CFA, CC, GAM
+* Raw Bayer input, YUV output: Full pipeline including CSC, CBHS/CBC, SUB
+* Non-RAW input (YUV/RGB sensor): Pipeline bypassed
diff --git a/MAINTAINERS b/MAINTAINERS
index 0efa8cc6775b..fe5c3bb03e60 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17052,6 +17052,7 @@ L:	linux-media@vger.kernel.org
 S:	Supported
 F:	Documentation/devicetree/bindings/media/atmel,isc.yaml
 F:	Documentation/devicetree/bindings/media/microchip,xisc.yaml
+F:	Documentation/userspace-api/media/drivers/microchip-isc.rst
 F:	drivers/media/platform/microchip/microchip-isc*
 F:	drivers/media/platform/microchip/microchip-sama*-isc*
 F:	drivers/staging/media/deprecated/atmel/atmel-isc*
-- 
2.34.1