Section 4 of the manual describes special files (devices).

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intel
Intel integrated graphics chipsets
intpm
Intel PIIX4 Power Management controller driver
intro
introduction to special files
intro
introduction to devices and device drivers
io
I/O privilege file
ip
Internet Protocol
ip6
Internet Protocol version 6 (IPv6) network layer
ipaccounting
ipfw — IP packet filter and traffic accounting
ipacct
ipfw — IP packet filter and traffic accounting
ipf
packet filtering kernel interface
ipfilter
Introduction to IP packet filtering
ipfirewall
ipfw — IP packet filter and traffic accounting
ipfw
IP packet filter and traffic accounting
ipheth
USB Apple iPhone/iPad tethered Ethernet driver
ipl
IP packet log device
ipmi
OpenIPMI compatible IPMI interface driver
ipnat
Network Address Translation kernel interface
ips
IBM/Adaptec ServeRAID controller driver
ipsec
Internet Protocol Security protocol
ipw
Intel PRO/Wireless 2100 IEEE 802.11 driver
ipwfw
Firmware Module for Intel PRO/Wireless 2100 driver
isci
Intel C600 Serial Attached SCSI driver
iscsi
iSCSI initiator
iscsi_initiator
kernel driver for the iSCSI protocol
iser
iSCSI Extensions for RDMA (iSER) driver
isl
Intersil(TM) I2C ISL29018 sensor driver
ismt
Intel SMBus Message Transport (SMBus 2.0) driver
isp
Qlogic based SPI and FibreChannel SCSI Host Adapters
ispfw
Firmware for Qlogic based SPI and FibreChannel SCSI Host Adapters
itwd
device driver for ITE Super I/O chips watchdog timer
iwi
Intel PRO/Wireless 2200BG/2225BG/2915ABG IEEE 802.11 driver
iwifw
Firmware Module for Intel PRO/Wireless 2200BG/2225BG/2915ABG driver
iwm
Intel IEEE 802.11ac wireless network driver
iwmfw
Firmware Module for Intel Wireless driver
iwn
Intel IEEE 802.11n wireless network driver
iwnfw
Firmware Module for Intel Wireless driver
ix
ixgbe — Intel(R) 10Gb Ethernet driver for the FreeBSD operating system
ixgbe
Intel(R) 10Gb Ethernet driver for the FreeBSD operating system
ixl
Intel Ethernet 700 Series Driver
jedec_dimm
report asset information and temperatures for JEDEC DDR3 / DDR4 DIMMs
jme
JMicron Gigabit/Fast Ethernet driver
joy
joystick device driver
joystick
Joystick input driver
kbd
Keyboard input driver
kbdmux
keyboard multiplexer
keyboard
pc keyboard interface
kld
dynamic kernel linker facility
kmem
mem, kmem, port - system memory, kernel memory and system ports
kmem
mem , kmem — memory files
ksyms
kernel symbol table interface
ksz8995ma
driver for Micrel KSZ8995MA fast ethernet switch chip
ktr
kernel tracing facility
kue
Kawasaki LSI KL5KUSB101B USB Ethernet driver
lagg
link aggregation and link failover interface
le
AMD Am7900 LANCE and Am79C9xx ILACC/PCnet Ethernet interface driver
led
API for manipulating LED's, lamps and other annunciators
lge
Level 1 LXT1001 NetCellerator PCI Gigabit Ethernet adapter driver
libinput
libinput-based X.Org input driver
linux
Linux ABI support
liquidio
Cavium 10Gb/25Gb Ethernet driver for the FreeBSD operating system
lirc
lirc devices
lm75
lm75 i2c digital temperature sensor driver
lo
software loopback network interface
longrun
Transmeta(TM) Crusoe(TM) LongRun(TM) support
loop-control
loop, loop-control - loop devices
loop
loop, loop-control - loop devices
loop
lo — software loopback network interface
lp
line printer devices
lp
printer port Internet Protocol driver
lpbb
parallel port I2C bit-banging interface
lpt
generic printer device driver
ltc430x
driver for LTC4305 and LTC4306 I2C mux chips
m-acr
ACR/NEMA medical image format (MedCon)
m-anlz
Analyze (SPM) medical image format (MedCon)
m-ecat
CTI ECAT 6/7 medical image format (MedCon)
m-gif
GIF87a and annimated GIF89a format (MedCon)
m-intf
InterFile 3.3 medical image format (MedCon)
m-inw
RUG INW1.0 medical image format (MedCon)
mac
Mandatory Access Control
mac_biba
Biba data integrity policy
mac_bsdextended
file system firewall policy
mac_ifoff
interface silencing policy
mac_lomac
Low-watermark Mandatory Access Control data integrity policy
mac_mls
Multi-Level Security confidentiality policy
mac_none
null MAC policy module
mac_ntpd
policy allowing ntpd to run as non-root user
mac_partition
process partition policy
mac_portacl
network port access control policy
mac_seeotheruids
simple policy controlling whether users see other users
mac_stub
MAC policy stub module
mac_test
MAC framework testing policy
malo
Marvell Libertas IEEE 802.11b/g wireless network driver
mce
mlx5en — Mellanox ConnectX-4, ConnectX-4 LX and ConnectX-5 based 100Gb, 50Gb, 40Gb, 25Gb and 10Gb Ethernet adapter driver
md
Multiple Device driver aka Linux Software RAID
md
memory disk
mdio
IEEE 802.3 Management Data Input/Output interface
me
encapsulating network device
mem
mem, kmem, port - system memory, kernel memory and system ports
mem
mem , kmem — memory files
meteor
video capture driver interface