Here is a list of all files with brief descriptions:

lib
compiler
armcc
errno.h	ARMCC specific error definitions
gcc
atomic.h	GCC specific atomic primitives for libmetal
compiler.h	GCC specific primitives for libmetal
iar
compiler.h	IAR specific primitives for libmetal
errno.h	IAR specific error definitions
processor
aarch64
cpu.h	Aarch64 CPU specific primitives
ceva
cpu.h	CEVA CPU specific primitives
generic
atomic.h	Generic environment atomic primitives for libmetal
cpu.h	Generic CPU specific primitives
hosted
cpu.c	Hosted libmetal cpu routines
cpu.h	Hosted environment CPU specific primitives
i686
atomic.h
cpu.h
ppc64
atomic.h
cpu.h
ppc64le
atomic.h
cpu.h
s390x
atomic.h
cpu.h
x86
cpu.h	X84 CPU specific primitives
x86_64
cpu.h	X86 64-bits CPU specific primitives
xtensa
cpu.h	Xtensa CPU specific primitives
system
freertos
template
sys.c	Machine specific system primitives implementation
alloc.h	FreeRTOS libmetal memory allocation definitions
assert.h	FreeRTOS assertion support
cache.h	FreeRTOS cache operation primitives for libmetal
condition.c	FreeRTOS libmetal condition variable handling
condition.h	FreeRTOS condition variable primitives for libmetal
device.c	FreeRTOS device operations
init.c	FreeRTOS libmetal initialization
io.c	FreeRTOS libmetal io operations
io.h	FreeRTOS specific io definitions
irq.c	FreeRTOS libmetal irq definitions
mutex.h	FreeRTOS mutex primitives for libmetal
shmem.c	FreeRTOS libmetal shared memory handling
sleep.h	FreeRTOS sleep primitives for libmetal
sys.h	FreeRTOS system primitives for libmetal
time.c	FreeRTOS libmetal time handling
generic
template
sys.c	Generic template system primitives implementation
alloc.h	Generic libmetal memory allocation definitions
assert.h	Generic assertion support
cache.h	Generic cache operation primitives for libmetal
condition.c	Generic libmetal condition variable handling
condition.h	Generic condition variable primitives for libmetal
device.c	Generic libmetal device operations
init.c	Generic libmetal initialization
io.c	Generic libmetal io operations
io.h	Generic specific io definitions
irq.c	Generic libmetal irq definitions
mutex.h	Generic mutex primitives for libmetal
shmem.c	Generic libmetal shared memory handling
sleep.h	Generic sleep primitives for libmetal
sys.h	Generic system primitives for libmetal
time.c	Generic libmetal time handling
linux
alloc.h	Linux memory allocation definitions
assert.h	Linux assertion support
cache.h	Linux cache operation primitives for libmetal
condition.c	Linux libmetal condition variable handling
condition.h	Linux condition variable primitives for libmetal
device.c	Linux libmetal device operations
init.c	Linux libmetal initialization
io.h	Linux specific io definitions
irq.c	Linux libmetal irq operations
irq.h	Linux libmetal irq definitions
mutex.h	Linux mutex primitives for libmetal
shmem.c	Linux libmetal shared memory handling
sleep.h	Linux sleep primitives for libmetal
sys.h	Linux system primitives for libmetal
time.c	Linux libmetal time handling
utilities.c	Linux libmetal utility functions
nuttx
alloc.h	NuttX libmetal memory allocation definitions
assert.h	NuttX assertion support
cache.h	NuttX cache operation primitives for libmetal
condition.c	NuttX libmetal condition variable handling
condition.h	NuttX condition variable primitives for libmetal
device.c	NuttX libmetal device definitions
init.c	NuttX libmetal initialization
io.c	NuttX libmetal io operations
io.h	NuttX specific io definitions
irq.c	NuttX libmetal irq definitions
irq.h	NuttX libmetal irq definitions
mutex.h	NuttX mutex primitives for libmetal
shmem.c	NuttX libmetal shared memory handling
sleep.h	NuttX sleep primitives for libmetal
sys.h	NuttX system primitives for libmetal
time.c	NuttX libmetal time handling
zephyr
alloc.c	Zephyr libmetal memory allocation handling
alloc.h	Zephyr libmetal memory allocation definitions
assert.h	Zephyr assertion support
cache.h	Zephyr cache operation primitives for libmetal
condition.c	Zephyr libmetal condition variable handling
condition.h	Zephyr condition variable primitives for libmetal
device.c	Zephyr libmetal device definitions
init.c	Zephyr libmetal initialization
io.h	Zephyr specific io definitions
irq.c	Zephyr libmetal irq definitions
log.c	Zephyr libmetal log handler
log.h	Zephyr libmetal log handler definition
mutex.h	Zephyr mutex primitives for libmetal
shmem.c	Zephyr libmetal shared memory handling
sleep.h	Zephyr sleep primitives for libmetal
sys.c	Zephyr system primitives for libmetal
sys.h	Zephyr system primitives for libmetal
time.c	Zephyr libmetal time handling
alloc.h	Memory allocation handling primitives for libmetal
assert.h	Assertion support
atomic.h	Atomic primitives for libmetal
cache.h	CACHE operation primitives for libmetal
compiler.h	Compiler specific primitives for libmetal
condition.h	Condition variable for libmetal
config.h	Generated configuration settings for libmetal
cpu.h	CPU primitives for libmetal
device.c	Libmetal bus abstraction definitions
device.h	Bus abstraction for libmetal
dma.c	Libmetal DMA primitives definitions
dma.h	DMA primitives for libmetal
errno.h	Error specific primitives for libmetal
init.c	Libmetal initialization
io.c	Libmetal I/O access primitives definition
io.h	I/O access primitives for libmetal
irq.c	Libmetal interrupt primitives definition
irq.h	Interrupt handling primitives for libmetal
irq_controller.h	Interrupt handling primitives for libmetal
list.h	List primitives for libmetal
log.c	Libmetal Logging primitives definition
log.h	Logging support for libmetal
mutex.h	Mutex primitives for libmetal
shmem.c	Generic libmetal shared memory handling
shmem.h	Shared memory primitives for libmetal
sleep.h	Sleep primitives for libmetal
softirq.c	Libmetal soft interrupt primitives definition
softirq.h	Soft Interrupt handling primitives for libmetal
spinlock.h	Spinlock primitives for libmetal
sys.h	System primitives for libmetal
time.h	Time primitives for libmetal
utilities.h	Utility routines for libmetal
version.c	Libmetal version information definition
version.h	Library version information for libmetal