v4.19.13 snapshot.
diff --git a/arch/x86/include/asm/serial.h b/arch/x86/include/asm/serial.h
new file mode 100644
index 0000000..ece8299
--- /dev/null
+++ b/arch/x86/include/asm/serial.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SERIAL_H
+#define _ASM_X86_SERIAL_H
+
+/*
+ * This assumes you have a 1.8432 MHz clock for your UART.
+ *
+ * It'd be nice if someone built a serial card with a 24.576 MHz
+ * clock, since the 16550A is capable of handling a top speed of 1.5
+ * megabits/second; but this requires a faster clock.
+ */
+#define BASE_BAUD (1843200/16)
+
+/* Standard COM flags (except for COM4, because of the 8514 problem) */
+#ifdef CONFIG_SERIAL_8250_DETECT_IRQ
+# define STD_COMX_FLAGS (UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_AUTO_IRQ)
+# define STD_COM4_FLAGS (UPF_BOOT_AUTOCONF | 0 | UPF_AUTO_IRQ)
+#else
+# define STD_COMX_FLAGS (UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | 0 )
+# define STD_COM4_FLAGS (UPF_BOOT_AUTOCONF | 0 | 0 )
+#endif
+
+#define SERIAL_PORT_DFNS \
+ /* UART CLK PORT IRQ FLAGS */ \
+ { .uart = 0, BASE_BAUD, 0x3F8, 4, STD_COMX_FLAGS }, /* ttyS0 */ \
+ { .uart = 0, BASE_BAUD, 0x2F8, 3, STD_COMX_FLAGS }, /* ttyS1 */ \
+ { .uart = 0, BASE_BAUD, 0x3E8, 4, STD_COMX_FLAGS }, /* ttyS2 */ \
+ { .uart = 0, BASE_BAUD, 0x2E8, 3, STD_COM4_FLAGS }, /* ttyS3 */
+
+#endif /* _ASM_X86_SERIAL_H */