This adds basic architectural support for the LPC546xx family and includes support for the LPCXpresso-LPC54628 board. The basic NSH port is almost complete... still lacking GPIO support and LED support. There are still no significant drivers available.

Squashed commit of the following:

    arch/arm/src/lpc54xx:  Finish off some missing logic.  Complete now execpt for GPIO and LED support.
    arch/arm/src/lpc54xx:  Add lpc54_clrpend.c
    arch/arm/src/lpc54xx:  Serial driver is complete and compiles.
    arch/arm/src/lpc54xx:  Add beginning of a serial driver (still missing some logic)
    arch/arm/src/lpc54xx:  Fleshes out low level USART intialization.
    arch/arm/src/lpc546xx/Kconfig: Add hooks to integrate with common seril upper half.
    arch/arm/src/lpc54xx:  Beginning of USART console support.
    arch/arm/src/lpc54xx: Completes very basic clock configuration.
    arch/arm/src/lpc54xx:  Add clocking logic (still not complete)
    arch/arm/src/lpc54xx:  Beginning of PLL configuration logic.
    arch/arm/src/lpc54xx:  Fix a few things from first compile attempt.  Compilation cannot work until I at least finish the clock configuration logic.
    arch/arm/src/lpc54xx: Addes some SysTick logic.
    arch/arm/src/lpc54xx:  Completes basic startup logic (sans clock configuration) and interrupt configuration.
     arch/arm/src/lpc54xx:  Add generic ARMv7-M start-up logic (needs LPC54628 customizations); add emtpy file that will eventually hold the clock configuration logic.
    arch/arm/src/lpc54xx:  Add (incomplete) SYSCON register definition header file.
    arch/arm/src/lpc54xx:  Add FLEXCOMM header file.
    arch/arm/src/lpc54xx:  Bring in tickless clock logic from LPC43; configs/lpcxpresso-lpc54628: mount procfs if enabled.
    arch/arm/src/lpc54xx: Add RIT clock definitions; add SysTick initialization (not finished)
    LPC54xx and LPCXpresso-LPC54628: add more boilerplate files and stubbed out files.
    arch/arm/src/lpc54xx:  Add (incomplete) USART header file.
    Add another condition to a Kconfig; refresh a defconfig.
    arch/arm/src/lpc54xx/chip: Add LPC54628 memory map header files.
    configs/lpcxpresso-lpc54628:  Add basic build files for the LPCXpresso-LPC54628
    arch/: Basic build directory structure for the LPC54628

drivers/serial/Kconfig

@@ -461,6 +461,11 @@ config USART8_SERIALDRIVER
 	default n
 	select MCU_SERIAL
 
+config USART9_SERIALDRIVER
+	bool
+	default n
+	select MCU_SERIAL
+
 config OTHER_UART_SERIALDRIVER
 	bool
 	default n
@@ -667,6 +672,11 @@ config USART8_SERIAL_CONSOLE
 	depends on USART8_SERIALDRIVER
 	select SERIAL_CONSOLE
 
+config USART9_SERIAL_CONSOLE
+	bool "USART8"
+	depends on USART9_SERIALDRIVER
+	select SERIAL_CONSOLE
+
 config SCI0_SERIAL_CONSOLE
 	bool "SCI0"
 	depends on SCI0_SERIALDRIVER
@@ -1924,6 +1934,71 @@ config UART8_DMA
 
 endmenu
 
+menu "USART9 Configuration"
+	depends on USART9_SERIALDRIVER
+
+config USART9_RXBUFSIZE
+	int "Receive buffer size"
+	default 256
+	---help---
+		Characters are buffered as they are received. This specifies
+		the size of the receive buffer.
+
+config USART9_TXBUFSIZE
+	int "Transmit buffer size"
+	default 256
+	---help---
+		Characters are buffered before being sent.  This specifies
+		the size of the transmit buffer.
+
+config USART9_BAUD
+	int "BAUD rate"
+	default 115200
+	---help---
+		The configured BAUD of the USART.
+
+config USART9_BITS
+	int "Character size"
+	default 8
+	---help---
+		The number of bits.  Must be either 7 or 8.
+
+config USART9_PARITY
+	int "Parity setting"
+	default 0
+	range 0 2
+	---help---
+		0=no parity, 1=odd parity, 2=even parity
+
+config USART9_2STOP
+	int "Uses 2 stop bits"
+	default 0
+	---help---
+		1=Two stop bits
+
+config USART9_IFLOWCONTROL
+	bool "USART9 RTS flow control"
+	default n
+	select SERIAL_IFLOWCONTROL
+	---help---
+		Enable USART9 RTS flow control
+
+config USART9_OFLOWCONTROL
+	bool "USART9 CTS flow control"
+	default n
+	select SERIAL_OFLOWCONTROL
+	---help---
+		Enable USART9 CTS flow control
+
+config USART9_DMA
+	bool "USART9 DMA support"
+	default n
+	select SERIAL_DMA
+	---help---
+		Enable DMA transfers on USART9
+
+endmenu
+
 menu "SCI0 Configuration"
 	depends on SCI0_SERIALDRIVER