diff --git a/src/machine/usb/adc/doc.go b/src/machine/usb/adc/doc.go
new file mode 100644
index 00000000..beed33c5
--- /dev/null
+++ b/src/machine/usb/adc/doc.go
@@ -0,0 +1,2 @@
+// package adc is for USB Audio Device Class devices.
+package adc
diff --git a/src/machine/usb/midi/buffer.go b/src/machine/usb/adc/midi/buffer.go
similarity index 100%
rename from src/machine/usb/midi/buffer.go
rename to src/machine/usb/adc/midi/buffer.go
diff --git a/src/machine/usb/midi/messages.go b/src/machine/usb/adc/midi/messages.go
similarity index 100%
rename from src/machine/usb/midi/messages.go
rename to src/machine/usb/adc/midi/messages.go
diff --git a/src/machine/usb/midi/midi.go b/src/machine/usb/adc/midi/midi.go
similarity index 100%
rename from src/machine/usb/midi/midi.go
rename to src/machine/usb/adc/midi/midi.go
diff --git a/src/machine/usb/midi/notes.go b/src/machine/usb/adc/midi/notes.go
similarity index 100%
rename from src/machine/usb/midi/notes.go
rename to src/machine/usb/adc/midi/notes.go
diff --git a/src/machine/usb/cdc/doc.go b/src/machine/usb/cdc/doc.go
new file mode 100644
index 00000000..0a375e46
--- /dev/null
+++ b/src/machine/usb/cdc/doc.go
@@ -0,0 +1,2 @@
+// package cdc is for USB Communication Device Class devices.
+package cdc
diff --git a/src/machine/usb/descriptor/doc.go b/src/machine/usb/descriptor/doc.go
new file mode 100644
index 00000000..f35a7681
--- /dev/null
+++ b/src/machine/usb/descriptor/doc.go
@@ -0,0 +1,3 @@
+// package descriptor is for the USB descriptor definitions.
+// For the actual implementations, see the individual packages.
+package descriptor
diff --git a/src/machine/usb/doc.go b/src/machine/usb/doc.go
new file mode 100644
index 00000000..03dbadc0
--- /dev/null
+++ b/src/machine/usb/doc.go
@@ -0,0 +1,4 @@
+// package usb contains the subpackages with USB descriptors and device
+// implementations for standard USB device classes such as the Communcation
+// Data Class (CDC), Human Interface Device (HID), and Audio Device Class (ADC).
+package usb
diff --git a/src/machine/usb/hid/doc.go b/src/machine/usb/hid/doc.go
new file mode 100644
index 00000000..82797a54
--- /dev/null
+++ b/src/machine/usb/hid/doc.go
@@ -0,0 +1,2 @@
+// package hid is for USB Human Interface Devices.
+package hid