docs: filesystems: sysfs: add remaining top level sysfs directory descriptions

Finish top level sysfs directory descriptions for block, class, firmware,
hypervisor, kernel, and power. Did not write one for net directory. See
commit bc3a88431672 ("docs: filesystems: sysfs: remove top level sysfs net
 directory")

Signed-off-by: Alex Tran <alex.t.tran@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20250902023039.1351270-1-alex.t.tran@gmail.com>

diff --git a/Documentation/filesystems/sysfs.rst b/Documentation/filesystems/sysfs.rst
index f1a776a7ac66bcaeee518f8a2f382561461df4ca..354c5fb310b46d5258195c46be728d4ec2716be8 100644 (file)
--- a/Documentation/filesystems/sysfs.rst
+++ b/Documentation/filesystems/sysfs.rst
@@ -334,8 +334,22 @@ a stat(2) operation.
 More information on driver-model specific features can be found in
 Documentation/driver-api/driver-model/.
 
+block/ contains symlinks to all the block devices discovered on the system.
+These symlinks point to directories under /sys/devices.
 
-TODO: Finish this section.
+class/ contains a directory for each device class, grouped by functional type.
+Each directory in class/ contains symlinks to devices in the /sys/devices directory.
+
+firmware/ contains system firmware data and configuration such as firmware tables,
+ACPI information, and device tree data.
+
+hypervisor/ contains virtualization platform information and provides an interface to
+the underlying hypervisor.  It is only present when running on a virtual machine.
+
+kernel/ contains runtime kernel parameters, configuration settings, and status.
+
+power/ contains power management subsystem information including
+sleep states, suspend/resume capabilities, and policies.
 
 
 Current Interfaces