Update device documentation

docs/models/dcim/device.md

@@ -1,7 +1,15 @@
 # Devices
 
-Every piece of hardware which is installed within a rack exists in NetBox as a device. Devices are measured in rack units (U) and can be half depth or full depth. A device may have a height of 0U: These devices do not consume vertical rack space and cannot be assigned to a particular rack unit. A common example of a 0U device is a vertically-mounted PDU.
+Every piece of hardware which is installed within a site or rack exists in NetBox as a device. Devices are measured in rack units (U) and can be half depth or full depth. A device may have a height of 0U: These devices do not consume vertical rack space and cannot be assigned to a particular rack unit. A common example of a 0U device is a vertically-mounted PDU.
 
 When assigning a multi-U device to a rack, it is considered to be mounted in the lowest-numbered rack unit which it occupies. For example, a 3U device which occupies U8 through U10 is said to be mounted in U8. This logic applies to racks with both ascending and descending unit numbering.
 
-A device is said to be full depth if its installation on one rack face prevents the installation of any other device on the opposite face within the same rack unit(s). This could be either because the device is physically too deep to allow a device behind it, or because the installation of an opposing device would impede airflow.
+A device is said to be full-depth if its installation on one rack face prevents the installation of any other device on the opposite face within the same rack unit(s). This could be either because the device is physically too deep to allow a device behind it, or because the installation of an opposing device would impede airflow.
+
+Each device must be instantiated from a pre-created device type, and its default components (console ports, power ports, interfaces, etc.) will be created automatically. (The device type associated with a device may be changed after its creation, however its components will not be updated retroactively.)
+
+Each device must be assigned a site, device role, and operational status, and may optionally be assigned to a specific rack within a site. A platform, serial number, and asset tag may optionally be assigned to each device.
+
+Device names must be unique within a site, unless the device has been assigned to a tenant. Devices may also be unnamed.
+
+When a device has one or more interfaces with IP addresses assigned, a primary IP for the device can be designated, for both IPv4 and IPv6.

docs/models/dcim/devicerole.md

@@ -1,3 +1,3 @@
 # Device Roles
 
-Devices can be organized by functional roles. These roles are fully customizable. For example, you might create roles for core switches, distribution switches, and access switches.
+Devices can be organized by functional roles, which are fully customizable by the user. For example, you might create roles for core switches, distribution switches, and access switches within your network.

docs/models/dcim/platform.md

@@ -1,7 +1,9 @@
 # Platforms
 
-A platform defines the type of software running on a device or virtual machine. This can be helpful when it is necessary to distinguish between, for instance, different feature sets. Note that two devices of the same type may be assigned different platforms: for example, one Juniper MX240 running Junos 14 and another running Junos 15.
+A platform defines the type of software running on a device or virtual machine. This can be helpful to model when it is necessary to distinguish between different versions or feature sets. Note that two devices of the same type may be assigned different platforms: For example, one Juniper MX240 might run Junos 14 while another runs Junos 15.
 
-The platform model is also used to indicate which [NAPALM](https://napalm-automation.net/) driver NetBox should use when connecting to a remote device. The name of the driver along with optional parameters are stored with the platform.
+Platforms may optionally be limited by manufacturer: If a platform is assigned to a particular manufacturer, it can only be assigned to devices with a type belonging to that manufacturer.
+
+The platform model is also used to indicate which [NAPALM](https://napalm-automation.net/) driver and any associated arguments NetBox should use when connecting to a remote device. The name of the driver along with optional parameters are stored with the platform.
 
 The assignment of platforms to devices is an optional feature, and may be disregarded if not desired.

docs/models/dcim/virtualchassis.md

@@ -1,5 +1,8 @@
 # Virtual Chassis
 
-A virtual chassis represents a set of devices which share a single control plane: a stack of switches which are managed as a single device, for example. Each device in the virtual chassis is assigned a position and (optionally) a priority. Exactly one device is designated the virtual chassis master: This device will typically be assigned a name, secrets, services, and other attributes related to its management.
+A virtual chassis represents a set of devices which share a common control plane. A common example of this is a stack of switches which are connected and configured to operate as a single device. A virtual chassis must be assigned a name and may be assigned a domain.
 
-It's important to recognize the distinction between a virtual chassis and a chassis-based device. For instance, a virtual chassis is not used to model a chassis switch with removable line cards such as the Juniper EX9208, as its line cards are _not_ physically separate devices capable of operating independently.
+Each device in the virtual chassis is referred to as a VC member, and assigned a position and (optionally) a priority. VC member devices commonly reside within the same rack, though this is not a requirement. One of the devices may be designated as the VC master: This device will typically be assigned a name, secrets, services, and other attributes related to managing the VC.
+
+!!! note
+    It's important to recognize the distinction between a virtual chassis and a chassis-based device. A virtual chassis is **not** suitable for modeling a chassis-based switch with removable line cards (such as the Juniper EX9208), as its line cards are _not_ physically autonomous devices.