scsi: leapraid: Add driver documentation

This patch adds the necessary documentation for the LeapRAID SCSI driver
to the kernel's documentation tree.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@kernel.org>
Signed-off-by: Dongdong Hao <doubled@leap-io-kernel.com>
Link: https://patch.msgid.link/6dc9239844dc00cd053ea0649cc9fe05cad1d98a.1785823793.git.doubled@leap-io-kernel.com
Signed-off-by: Martin K. Petersen (Oracle) <mkp@kernel.org>

Documentation/scsi/index.rst

@@ -56,6 +56,7 @@ SCSI host adapter drivers
    g_NCR5380
    hpsa
    hptiop
+   leapraid
    libsas
    lpfc
    megaraid

Documentation/scsi/leapraid.rst

@@ -0,0 +1,110 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
+LeapRAID Driver for Linux
+=========================
+
+Introduction
+============
+
+LeapRAID is a storage RAID controller driver developed by LeapIO Tech Inc. The
+controller targets enterprise storage, cloud infrastructure, high performance
+computing (HPC), and AI workloads.
+
+It provides high-performance storage virtualization over PCI Express Gen4
+and supports both SAS and SATA HDDs and SSDs. It offers both Host Bus Adapter
+and RAID modes to meet diverse deployment requirements.
+
+Supported devices
+=================
+
+- LeapHBA-8200C
+
+Features
+========
+- PCIe Gen4 x8 host interface
+- Support for SAS and SATA devices
+- RAID levels: 0, 1, 10, 5, 50, 6, 60
+- Advanced error handling and end-to-end data integrity
+
+LeapRAID specific host attributes
+=================================
+
+::
+
+   /sys/class/scsi_host/host*/fw_queue_depth
+   /sys/class/scsi_host/host*/host_sas_address
+   /sys/class/scsi_host/host*/board_name
+
+The host "fw_queue_depth" read-only attribute shows the firmware queue
+depth of the host.
+
+The host "host_sas_address" read-only attribute shows the SAS address
+of the host.
+
+The host "board_name" read-only attribute shows the board name reported
+by manufacturing page 0.
+
+LeapRAID specific disk attributes
+=================================
+
+::
+
+   /sys/class/scsi_disk/host:bus:target:lun/device/sas_device_handle
+   /sys/class/scsi_disk/host:bus:target:lun/device/ncq_cmd_prio_enable
+
+The read-only attribute "sas_device_handle" represents the disk's device
+handle, which is a unique identifier maintained by the firmware.
+
+This attribute "ncq_cmd_prio_enable" controls NCQ command priority. A value
+of 0 disables NCQ priority handling for RT-priority I/O. Writing 1 enables
+NCQ priority handling when the device reports support for the feature through
+VPD page 0x89. Unsupported devices keep the effective state at 0.
+
+LeapRAID module parameters
+==========================
+
+The following module parameters can be configured at driver load time to
+control driver behavior and tuning options.
+
+1. open_pcie_trace
+------------------
+
+This parameter controls whether PCIe transaction tracing is enabled in the
+driver. When set to 1, PCIe trace collection is enabled by default, allowing
+detailed tracing of PCIe operations for debugging and performance analysis.
+Setting it to 0 disables the trace functionality to reduce overhead in
+production environments.
+
+2. enable_mp
+------------
+
+This parameter enables or disables multipath support for target devices.
+When set to 1, multipath functionality is enabled (default), allowing
+multiple paths to be established. Setting it to 0 disables multipath
+handling.
+
+3. max_msix_vectors
+-------------------
+
+This parameter sets the upper limit on the number of MSI-X interrupt
+vectors that the driver will request during initialization. The default
+value of -1 allows the driver to use all available vectors as provided
+by the device. Setting a positive integer restricts the number of vectors.
+
+4. poll_queues
+--------------
+
+This parameter specifies the number of I/O queues to be used when operating
+in io_uring poll mode. The default value is 0.
+
+File Location
+=============
+The driver source is located at:
+
+``drivers/scsi/leapraid/``
+
+.. note::
+
+   This document is intended for kernel developers and system
+   integrators who need to build, test, and deploy the LeapRAID driver.