PCI Serial Parameters. It is an array of VendorID, DeviceID, ClockRate, Offset,
BarIndex, RegisterStride, ReceiveFifoDepth, TransmitFifoDepth information that
describes the parameters of special PCI serial devices.
Each array entry is 24-byte in length. The array is terminated
by an array entry with a PCI Vendor ID of 0xFFFF. If a platform only contains a
standard 16550 PCI serial device whose class code is 7/0/2, the value is 0xFFFF.
The C style structure is defined as below:

typedef struct {

UINT16 VendorId; ///< Vendor ID to match the PCI device. The value 0xFFFF terminates the list of entries.

UINT16 DeviceId; ///< Device ID to match the PCI device.

UINT32 ClockRate; ///< UART clock rate. Set to 0 for default clock rate of 1843200 Hz.

UINT64 Offset; ///< The byte offset into to the BAR.

UINT8 BarIndex; ///< Which BAR to get the UART base address.

UINT8 RegisterStride; ///< UART register stride in bytes. Set to 0 for default register stride of 1 byte.

UINT16 ReceiveFifoDepth; ///< UART receive FIFO depth in bytes. Set to 0 for a default FIFO depth of 16 bytes.

UINT16 TransmitFifoDepth; ///< UART transmit FIFO depth in bytes. Set to 0 for a default FIFO depth of 16 bytes.

UINT8 Reserved[2];

} PCI_SERIAL_PARAMETER;

It contains zero or more instances of the above structure.

For example, if a PCI device contains two UARTs, PcdPciSerialParameters needs
to contain two instances of the above structure, with the VendorId and DeviceId
equals to the Device ID and Vendor ID of the device; If the PCI device uses the
first two BARs to support two UARTs, BarIndex of first instance equals to 0 and
BarIndex of second one equals to 1; If the PCI device uses the first BAR to
support both UARTs, BarIndex of both instance equals to 0, Offset of first
instance equals to 0 and Offset of second one equals to a value bigger than or
equal to 8.

For certain UART whose register needs to be accessed in DWORD aligned address,
RegisterStride equals to 4.
Pci Serial Parameters

PCD Information

Name	Token Space	Token number	Data Type	Default Value
PcdPciSerialParameters	gEfiMdeModulePkgTokenSpaceGuid	0x00010071	VOID*	{0xFF, 0xFF}